Marcus Aurelius Antoninus (Latin: [ˈmaːrkʊs au̯ˈreːliʊs antoːˈniːnʊs]; English: /ɔːˈriːliəs/ or-EE-lee-əs; 26 April 121 – 17 March 180) was Roman emperor from 161 to 180 and a Stoic philosopher. He was a member of the Nerva–Antonine dynasty, the last of the rulers later known as the Five Good Emperors and the last emperor of the Pax Romana, an age of relative peace, calm, and stability for the Roman Empire lasting from 27 BC to 180 AD. He served as Roman consul in 140, 145, and 161.

Marcus Aurelius was the son of the praetor Marcus Annius Verus and his wife, Domitia Calvilla. He was related through marriage to the emperors Trajan and Hadrian. Marcus was three when his father died, and was raised by his mother and paternal grandfather. After Hadrian's adoptive son, Aelius Caesar, died in 138, Hadrian adopted Marcus's uncle Antoninus Pius as his new heir. In turn, Antoninus adopted Marcus and Lucius, the son of Aelius. Hadrian died that year, and Antoninus became emperor. Now heir to the throne, Marcus studied Greek and Latin under tutors such as Herodes Atticus and Marcus Cornelius Fronto. He married Antoninus's daughter Faustina in 145.

After Antoninus died in 161, Marcus acceded to the throne alongside his adoptive brother, who took the regnal name Lucius Aurelius Verus. Under the reign of Marcus Aurelius, the Roman Empire witnessed much military conflict. In the East, the Romans fought the Parthian war of Lucius Verus with a revitalized Parthian Empire and the rebel Kingdom of Armenia. Marcus defeated the Marcomanni, Quadi, and Sarmatian Iazyges in the Marcomannic Wars. These and other Germanic peoples began to represent a troubling reality for the Empire. He reduced the silver purity of the Roman currency, the denarius. The persecution of Christians in the Roman Empire appears to have increased during his reign, but his involvement in this is unlikely since there is no record of early Christians in the 2nd century calling him a persecutor, and Tertullian even called Marcus a "protector of Christians". The Antonine Plague broke out in 165 or 166 and devastated the population of the Roman Empire, causing the deaths of five to ten million people. Lucius Verus may have died from the plague in 169. When Marcus himself died in 180, he was succeeded by his son Commodus.

Commodus's succession after Marcus has been a subject of debate among both contemporary and modern historians. The Column of Marcus Aurelius and Equestrian Statue of Marcus Aurelius still stand in Rome, where they were erected in celebration of his military victories. Meditations, the writings of "the philosopher" – as contemporary biographers called Marcus – are a significant source of the modern understanding of ancient Stoic philosophy. These writings have been praised by fellow writers, philosophers, monarchs, and politicians centuries after his death.

The major sources depicting the life and rule of Marcus Aurelius are patchy and frequently unreliable. The most important group of sources, the biographies contained in the Historia Augusta, claimed to be written by a group of authors at the turn of the 4th century AD, but it is believed they were in fact written by a single author (referred to here as 'the biographer') from about 395. The later biographies and the biographies of subordinate emperors and usurpers are unreliable, but the earlier biographies, derived primarily from now-lost earlier sources (Marius Maximus or Ignotus), are considered to be more accurate. For Marcus's life and rule, the biographies of Hadrian, Antoninus, Marcus, and Lucius are largely reliable, but those of Aelius Verus and Avidius Cassius are not.

A body of correspondence between Marcus's tutor Fronto and various Antonine officials survives in a series of patchy manuscripts, covering the period from c. 138 to 166. Marcus's own Meditations offer a window on his inner life, but are largely undateable and make few specific references to worldly affairs. The main narrative source for the period is Cassius Dio, a Greek senator from Bithynian Nicaea who wrote a history of Rome from its founding to 229 in eighty books. Dio is vital for the military history of the period, but his senatorial prejudices and strong opposition to imperial expansion obscure his perspective. Some other literary sources provide specific details: the writings of the physician Galen on the habits of the Antonine elite, the orations of Aelius Aristides on the temper of the times, and the constitutions preserved in the Digest and Codex Justinianeus on Marcus's legal work. Inscriptions and coin finds supplement the literary sources.

Marcus was born in Rome on 26 April 121. His birth name is sometimes given as Marcus Annius Verus, but sources assign this name to him upon his father's death and unofficial adoption by his grandfather, upon his coming of age. He may have been known as "Marcus Annius Catilius Severus", at birth or some point in his youth, or "Marcus Catilius Severus Annius Verus". Upon his adoption by Antoninus as heir to the throne, he was known as "Marcus Aelius Aurelius Verus Caesar" and, upon his ascension, he was "Marcus Aurelius Antoninus Augustus" until his death; Epiphanius of Salamis, in his chronology of the Roman emperors included in his On Weights and Measures, calls him Marcus Aurelius Verus.

The father of Marcus Aurelius was Marcus Annius Verus (III). His gens Annia was of Italic origin, but settled at some point in the small colony of Ucubi (Colonia Claritas Iulia Ucubi) south-east of Córdoba in Iberian Baetica (modern Andalusia, Spain); the gens had legendary claims of descendance from Numa Pompilius. The Annii Veri rose to prominence in Rome in the late 1st century AD. Marcus's great-grandfather Marcus Annius Verus (I) was a senator and (according to the Historia Augusta) ex-praetor; his grandfather Marcus Annius Verus (II) was made patrician in 73–74. Through his grandmother Rupilia Faustina, Marcus was related to the Nerva-Antonine dynasty; Rupilla was the step-daughter of Salonia Matidia, who was the niece of the emperor Trajan.

Marcus's mother, Domitia Lucilla Minor (also known as Domitia Calvilla), was the daughter of the Roman patrician P. Calvisius Tullus and inherited a great fortune (described at length in one of Pliny's letters) from her parents and grandparents. Her inheritance included large brickworks on the outskirts of Rome – a profitable enterprise in an era when the city was experiencing a construction boom – and the Horti Domitia Calvillae (or Lucillae), a villa on the Caelian hill of Rome. Marcus himself was born and raised in the Horti and referred to the Caelian hill as 'My Caelian'.

The adoptive family of Marcus was the gens Aurelia, an old Roman gens. His adoptive father Antoninus Pius came from the Aurelii Fulvi, a branch of the Aurelii settled in the colony of Nemausus in Roman Gaul.

Marcus's sister, Annia Cornificia Faustina, was probably born in 122 or 123. His father probably died in 125 or 126 when Marcus was three years old during his praetorship. Though he can hardly have known his father, Marcus wrote in his Meditations that he had learned 'modesty and manliness' from his memories of his father and the man's posthumous reputation. His mother Lucilla did not remarry and, following prevailing aristocratic customs, probably did not spend much time with her son. Instead, Marcus was in the care of 'nurses', and was raised after his father's death by his grandfather Marcus Annius Verus (II), who had always retained the legal authority of patria potestas over his son and grandson. Technically this was not an adoption, the creation of a new and different patria potestas. Lucius Catilius Severus, described as Marcus's maternal great-grandfather, also participated in his upbringing; he was probably the elder Domitia Lucilla's stepfather. Marcus was raised in his parents' home on the Caelian Hill, an upscale area with few public buildings but many aristocratic villas. Marcus's grandfather owned a palace beside the Lateran, where he would spend much of his childhood. Marcus thanks his grandfather for teaching him 'good character and avoidance of bad temper'. He was less fond of the mistress his grandfather took and lived with after the death of his wife Rupilia. Marcus was grateful that he did not have to live with her longer than he did.

From a young age, Marcus displayed enthusiasm for wrestling and boxing. He trained in wrestling as a youth and into his teenage years, learned to fight in armour and joined the Salii, an order of priests dedicated to the god Mars that were responsible for the sacred shields, called Ancilia, and possibly for heralding war season's beginning and end. Marcus was educated at home, in line with contemporary aristocratic trends; he thanks Catilius Severus for encouraging him to avoid public schools. One of his teachers, Diognetus, a painting master, proved particularly influential; he seems to have introduced Marcus Aurelius to the philosophic way of life. In April 132, at the behest of Diognetus, Marcus took up the dress and habits of the philosopher: he studied while wearing a rough Greek cloak, and would sleep on the ground until his mother persuaded him to sleep on a bed. A new set of tutors – the Homeric scholar Alexander of Cotiaeum along with Trosius Aper and Tuticius Proculus, teachers of Latin – took over Marcus's education in about 132 or 133. Marcus thanks Alexander for his training in literary styling. Alexander's influence – an emphasis on matter over style and careful wording, with the occasional Homeric quotation – has been detected in Marcus's Meditations.

In late 136, Hadrian almost died from a hemorrhage. Convalescent in his villa at Tivoli, he selected Lucius Ceionius Commodus, Marcus's intended father-in-law, as his successor and adopted son, according to the biographer 'against the wishes of everyone'. While his motives are not certain, it would appear that his goal was to eventually place the then-too-young Marcus on the throne. As part of his adoption, Commodus took the name, Lucius Aelius Caesar. His health was so poor that, during a ceremony to mark his becoming heir to the throne, he was too weak to lift a large shield on his own. After a brief stationing on the Danube frontier, Aelius returned to Rome to make an address to the Senate on the first day of 138. However, the night before the scheduled speech, he grew ill and died of a hemorrhage later in the day.

On 24 January 138, Hadrian selected Aurelius Antoninus, the husband of Marcus's aunt Faustina the Elder, as his new successor. As part of Hadrian's terms, Antoninus, in turn, adopted Marcus and Lucius Commodus, the son of Lucius Aelius. Marcus became M. Aelius Aurelius Verus, and Lucius became L. Aelius Aurelius Commodus. At Hadrian's request, Antoninus's daughter Faustina was betrothed to Lucius. Marcus reportedly greeted the news that Hadrian had become his adoptive grandfather with sadness, instead of joy. Only with reluctance did he move from his mother's house on the Caelian to Hadrian's private home.

At some time in 138, Hadrian requested in the Senate that Marcus be exempt from the law barring him from becoming quaestor before his twenty-fourth birthday. The Senate complied, and Marcus served under Antoninus, the consul for 139. Marcus's adoption diverted him from the typical career path of his class. If not for his adoption, he probably would have become triumvir monetalis, a highly regarded post involving token administration of the state mint; after that, he could have served as tribune with a legion, becoming the legion's nominal second-in-command. Marcus probably would have opted for travel and further education instead. As it was, Marcus was set apart from his fellow citizens. Nonetheless, his biographer attests that his character remained unaffected: 'He still showed the same respect to his relations as he had when he was an ordinary citizen, and he was as thrifty and careful of his possessions as he had been when he lived in a private household'.

After a series of suicide attempts, all thwarted by Antoninus, Hadrian left for Baiae, a seaside resort on the Campanian coast. His condition did not improve, and he abandoned the diet prescribed by his doctors, indulging himself in food and drink. He sent for Antoninus, who was at his side when he died on 10 July 138. His remains were buried quietly at Puteoli. The succession to Antoninus was peaceful and stable: Antoninus kept Hadrian's nominees in office and appeased the senate, respecting its privileges and commuting the death sentences of men charged in Hadrian's last days. For his dutiful behaviour, Antoninus was asked to accept the name 'Pius'.

Immediately after Hadrian's death, Antoninus approached Marcus and requested that his marriage arrangements be amended: Marcus's betrothal to Ceionia Fabia would be annulled, and he would be betrothed to Faustina, Antoninus's daughter, instead. Faustina's betrothal to Ceionia's brother Lucius Commodus would also have to be annulled. Marcus consented to Antoninus's proposal. He was made consul for 140 with Antoninus as his colleague, and was appointed as a sevir, one of the knights' six commanders, at the order's annual parade on 15 July 139. As the heir apparent, Marcus became princeps iuventutis, head of the equestrian order. He now took the name Marcus Aelius Aurelius Verus Caesar. Marcus would later caution himself against taking the name too seriously: 'See that you do not turn into a Caesar; do not be dipped into the purple dye – for that can happen'. At the senate's request, Marcus joined all the priestly colleges (pontifices, augures, quindecimviri sacris faciundis, septemviri epulonum, etc.); direct evidence for membership, however, is available only for the Arval Brethren.

Antoninus demanded that Marcus reside in the House of Tiberius, the imperial palace on the Palatine, and take up the habits of his new station, the aulicum fastigium or 'pomp of the court', against Marcus's objections. Marcus would struggle to reconcile the life of the court with his philosophic yearnings. He told himself it was an attainable goal – 'Where life is possible, then it is possible to live the right life; life is possible in a palace, so it is possible to live the right life in a palace' – but he found it difficult nonetheless. He would criticize himself in the Meditations for 'abusing court life' in front of company.

As quaestor, Marcus would have had little real administrative work to do. He would read imperial letters to the senate when Antoninus was absent and would do secretarial work for the senators. But he felt drowned in paperwork and complained to his tutor, Marcus Cornelius Fronto: 'I am so out of breath from dictating nearly thirty letters'. He was being 'fitted for ruling the state', in the words of his biographer. He was required to make a speech to the assembled senators as well, making oratorical training essential for the job.

On 1 January 145, Marcus was made consul a second time. Fronto urged him in a letter to have plenty of sleep 'so that you may come into the Senate with a good colour and read your speech with a strong voice'. Marcus had complained of an illness in an earlier letter: 'As far as my strength is concerned, I am beginning to get it back; and there is no trace of the pain in my chest. But that ulcer [...] I am having treatment and taking care not to do anything that interferes with it'. Never particularly healthy or strong, Marcus was praised by Cassius Dio, writing of his later years, for behaving dutifully in spite of his various illnesses. In April 145, Marcus married Faustina, legally his sister, as had been planned since 138. Little is specifically known of the ceremony, but the biographer calls it 'noteworthy'. Coins were issued with the heads of the couple, and Antoninus, as Pontifex Maximus, would have officiated. Marcus makes no apparent reference to the marriage in his surviving letters, and only sparing references to Faustina.

After taking the toga virilis in 136, Marcus probably began his training in oratory. He had three tutors in Greek (Aninus Macer, Caninius Celer, and Herodes Atticus) and one in Latin (Marcus Cornelius Fronto). The latter two were the most esteemed orators of their time, but probably did not become his tutors until his adoption by Antoninus in 138. The preponderance of Greek tutors indicates the importance of the Greek language to the aristocracy of Rome. This was the age of the Second Sophistic, a renaissance in Greek letters. Although educated in Rome, in his Meditations Marcus would write his inmost thoughts in Greek.

Atticus was controversial: an enormously rich Athenian (probably the richest man in the eastern half of the empire), he was quick to anger and resented by his fellow Athenians for his patronizing manner. Atticus was an inveterate opponent of Stoicism and philosophic pretensions. He thought the Stoics' desire for apatheia was foolish: they would live a 'sluggish, enervated life', he said. In spite of the influence of Atticus, Marcus would later become a Stoic. He would not mention Herodes at all in his Meditations, in spite of the fact that they would come into contact many times over the following decades.

Fronto was highly esteemed: in the self-consciously antiquarian world of Latin letters, he was thought of as second only to Cicero, perhaps even an alternative to him. He did not care much for Atticus, though Marcus was eventually to put the pair on speaking terms. Fronto exercised a complete mastery of Latin, capable of tracing expressions through the literature, producing obscure synonyms, and challenging minor improprieties in word choice.

A significant amount of the correspondence between Fronto and Marcus has survived. The pair were very close, using intimate language such as 'Farewell my Fronto, wherever you are, my most sweet love and delight. How is it between you and me? I love you and you are not here' in their correspondence. Marcus spent time with Fronto's wife and daughter, both named Cratia, and they enjoyed light conversation.

He wrote Fronto a letter on his birthday, claiming to love him as he loved himself, and calling on the gods to ensure that every word he learnt of literature, he would learn 'from the lips of Fronto'. His prayers for Fronto's health were more than conventional, because Fronto was frequently ill; at times, he seems to be an almost constant invalid, always suffering – about one-quarter of the surviving letters deal with the man's sicknesses. Marcus asks that Fronto's pain be inflicted on himself, 'of my own accord with every kind of discomfort'.

Fronto never became Marcus's full-time teacher and continued his career as an advocate. One notorious case brought him into conflict with Atticus. Marcus pleaded with Fronto, first with 'advice', then as a 'favour', not to attack Atticus; he had already asked Atticus to refrain from making the first blows. Fronto replied that he was surprised to discover Marcus counted Atticus as a friend (perhaps Atticus was not yet Marcus's tutor), and allowed that Marcus might be correct, but nonetheless affirmed his intent to win the case by any means necessary: '[T]he charges are frightful and must be spoken of as frightful. Those in particular that refer to the beating and robbing I will describe so that they savour of gall and bile. If I happen to call him an uneducated little Greek it will not mean war to the death'. The outcome of the trial is unknown.

By the age of twenty-five (between April 146 and April 147), Marcus had grown disaffected with his studies in jurisprudence, and showed some signs of general malaise. His master, he writes to Fronto, was an unpleasant blowhard, and had made 'a hit at' him: 'It is easy to sit yawning next to a judge, he says, but to be a judge is noble work'. Marcus had grown tired of his exercises, of taking positions in imaginary debates. When he criticized the insincerity of conventional language, Fronto took to defend it. In any case, Marcus's formal education was now over. He had kept his teachers on good terms, following them devotedly. It 'affected his health adversely', his biographer writes, to have devoted so much effort to his studies. It was the only thing the biographer could find fault with in Marcus's entire boyhood.

Fronto had warned Marcus against the study of philosophy early on: "It is better never to have touched the teaching of philosophy [...] than to have tasted it superficially, with the edge of the lips, as the saying is". He disdained philosophy and philosophers and looked down on Marcus's sessions with Apollonius of Chalcedon and others in this circle. Fronto put an uncharitable interpretation of Marcus's 'conversion to philosophy': 'In the fashion of the young, tired of boring work', Marcus had turned to philosophy to escape the constant exercises of oratorical training. Marcus kept in close touch with Fronto, but would ignore Fronto's scruples.

Apollonius may have introduced Marcus to Stoic philosophy, but Quintus Junius Rusticus would have the strongest influence on the boy. He was the man Fronto recognized as having 'wooed Marcus away' from oratory. He was older than Fronto and twenty years older than Marcus. As the grandson of Arulenus Rusticus, one of the martyrs to the tyranny of Domitian (r. 81–96), he was heir to the tradition of 'Stoic Opposition' to the 'bad emperors' of the 1st century; the true successor of Seneca (as opposed to Fronto, the false one). Marcus thanks Rusticus for teaching him 'not to be led astray into enthusiasm for rhetoric, for writing on speculative themes, for discoursing on moralizing texts.... To avoid oratory, poetry, and 'fine writing''.

Philostratus describes how even when Marcus was an old man, in the latter part of his reign, he studied under Sextus of Chaeronea:

The Emperor Marcus was an eager disciple of Sextus the Boeotian philosopher, being often in his company and frequenting his house. Lucius, who had just come to Rome, asked the Emperor, whom he met on his way, where he was going to and on what errand, and Marcus answered, ' it is good even for an old man to learn; I am now on my way to Sextus the philosopher to learn what I do not yet know.' And Lucius, raising his hand to heaven, said, ' O Zeus, the king of the Romans in his old age takes up his tablets and goes to school.'

On 30 November 147, Faustina gave birth to a girl named Domitia Faustina. She was the first of at least thirteen children (including two sets of twins) that Faustina would bear over the next twenty-three years. The next day, 1 December, Antoninus gave Marcus the tribunician power and the imperium – authority over the armies and provinces of the emperor. As tribune, he had the right to bring one measure before the senate after the four Antoninus could introduce. His tribunician powers would be renewed with Antoninus's on 10 December 147. The first mention of Domitia in Marcus's letters reveals her as a sickly infant. 'Caesar to Fronto. If the gods are willing we seem to have a hope of recovery. The diarrhea has stopped, the little attacks of fever have been driven away. But the emaciation is still extreme and there is still quite a bit of coughing'. He and Faustina, Marcus wrote, had been 'pretty occupied' with the girl's care. Domitia would die in 151.

In 149, Faustina gave birth again, to twin sons. Contemporary coinage commemorates the event, with crossed cornucopiae beneath portrait busts of the two small boys, and the legend temporum felicitas, 'the happiness of the times'. They did not survive long. Before the end of the year, another family coin was issued: it shows only a tiny girl, Domitia Faustina, and one boy baby. Then another: the girl alone. The infants were buried in the Mausoleum of Hadrian, where their epitaphs survive. They were called Titus Aurelius Antoninus and Tiberius Aelius Aurelius. Marcus steadied himself: 'One man prays: 'How I may not lose my little child', but you must pray: 'How I may not be afraid to lose him'. He quoted from the Iliad what he called the "briefest and most familiar saying [...] enough to dispel sorrow and fear":

 leaves,
the wind scatters some on the face of the ground;
like unto them are the children of men.

– Iliad vi.146

Another daughter was born on 7 March 150, Annia Aurelia Galeria Lucilla. At some time between 155 and 161, probably soon after 155, Marcus's mother Domitia Lucilla died. Faustina probably had another daughter in 151, but the child, Annia Galeria Aurelia Faustina, might not have been born until 153. Another son, Tiberius Aelius Antoninus, was born in 152. A coin issue celebrates fecunditati Augustae, 'to Augusta's fertility', depicting two girls and an infant. The boy did not survive long, as evidenced by coins from 156, only depicting the two girls. He might have died in 152, the same year as Marcus's sister Cornificia. By 28 March 158, when Marcus replied, another of his children was dead. Marcus thanked the temple synod, 'even though this turned out otherwise'. The child's name is unknown. In 159 and 160, Faustina gave birth to daughters: Fadilla and Cornificia, named respectively after Faustina's and Marcus's dead sisters.

Lucius started his political career as a quaestor in 153. He was consul in 154, and was consul again with Marcus in 161. Lucius had no other titles, except that of 'son of Augustus'. Lucius had a markedly different personality from Marcus: he enjoyed sports of all kinds, but especially hunting and wrestling; he took obvious pleasure in the circus games and gladiatorial fights. He did not marry until 164.

In 156, Antoninus turned 70. He found it difficult to keep himself upright without stays. He started nibbling on dry bread to give him the strength to stay awake through his morning receptions. As Antoninus aged, Marcus would take on more administrative duties, more still when he became the praetorian prefect (an office that was as much secretarial as military) when Marcus Gavius Maximus died in 156 or 157. In 160, Marcus and Lucius were designated joint consuls for the following year. Antoninus may have already been ill.

Two days before his death, the biographer reports, Antoninus was at his ancestral estate at Lorium, in Etruria, about 19 kilometres (12 mi) from Rome. He ate Alpine cheese at dinner quite greedily. In the night he vomited; he had a fever the next day. The day after that, 7 March 161, he summoned the imperial council, and passed the state and his daughter to Marcus. The emperor gave the keynote to his life in the last word that he uttered when the tribune of the night-watch came to ask the password – 'aequanimitas' (equanimity). He then turned over, as if going to sleep, and died. His death closed out the longest reign since Augustus, surpassing Tiberius by a couple of months.

After Antoninus died in 161, Marcus was effectively sole ruler of the Empire. The formalities of the position would follow. The Senate would soon grant him the name Augustus and the title imperator, and he would soon be formally elected as pontifex maximus, chief priest of the official cults. Marcus made some show of resistance: the biographer writes that he was 'compelled' to take imperial power. This may have been a genuine horror imperii, 'fear of imperial power'. Marcus, with his preference for the philosophic life, found the imperial office unappealing. His training as a Stoic however, had made the choice clear to him that it was his duty.

Although Marcus showed no personal affection for Hadrian (significantly, he does not thank him in the first book of his Meditations), he presumably believed it his duty to enact the man's succession plans. Thus, although the Senate planned to confirm Marcus alone, he refused to take office unless Lucius received equal powers. The Senate accepted, granting Lucius the imperium, the tribunician power, and the title Augustus. Marcus became, in official titulature, Imperator Caesar Marcus Aurelius Antoninus Augustus; Lucius, forgoing his name Commodus and taking Marcus's family name Verus, became Imperator Caesar Lucius Aurelius Verus Augustus. It was the first time that Rome was ruled by two emperors.

In spite of their nominal equality, Marcus held more auctoritas, or 'authority', than Lucius. He had been consul once more than Lucius, he had shared in Antoninus's rule, and he alone was pontifex maximus. It would have been clear to the public which emperor was the more senior. As the biographer wrote: "Verus obeyed Marcus [...] as a lieutenant obeys a proconsul or a governor obeys the emperor".

Immediately after their Senate confirmation, the emperors proceeded to the Castra Praetoria, the camp of the Praetorian Guard. Lucius addressed the assembled troops, which then acclaimed the pair as imperatores. Then, like every new emperor since Claudius, Lucius promised the troops a special donativum. This donative, however, was twice the size of those past: 20,000 sesterces (5,000 denarii) per capita, with more to officers. In return for this bounty, equivalent to several years' pay, the troops swore an oath to protect the emperors. The ceremony was perhaps not entirely necessary, given that Marcus's accession had been peaceful and unopposed, but it was good insurance against later military troubles. Upon his accession he also devalued the Roman currency. He decreased the silver purity of the denarius from 83.5% to 79% – the silver weight dropping from 2.68 g (0.095 oz) to 2.57 g (0.091 oz).

Antoninus's funeral ceremonies were, in the words of the biographer, 'elaborate'. If his funeral followed those of his predecessors, his body would have been cremated on a pyre at the Campus Martius, and his spirit would have been seen as ascending to the gods' home in the heavens. Marcus and Lucius nominated their father for deification. In contrast to their behaviour during Antoninus's campaign to deify Hadrian, the Senate did not oppose the emperors' wishes. A flamen, or cultic priest, was appointed to minister the cult of the deified Divus Antoninus. Antoninus's remains were laid to rest in Hadrian's mausoleum, beside the remains of Marcus's children and of Hadrian himself. The temple he had dedicated to his wife, Diva Faustina, became the Temple of Antoninus and Faustina. It survives as the church of San Lorenzo in Miranda.

In accordance with his will, Antoninus's fortune passed on to Faustina. (Marcus had little need of his wife's fortune. Indeed, at his accession, Marcus transferred part of his mother's estate to his nephew, Ummius Quadratus.) Faustina was three months pregnant at her husband's accession. During the pregnancy she dreamed of giving birth to two serpents, one fiercer than the other. On 31 August, she gave birth at Lanuvium to twins: T. Aurelius Fulvus Antoninus and Lucius Aurelius Commodus. Aside from the fact that the twins shared Caligula's birthday, the omens were favorable, and the astrologers drew positive horoscopes for the children. The births were celebrated on the imperial coinage.

Soon after the emperor's accession, Marcus's eleven-year-old daughter, Annia Lucilla, was betrothed to Lucius (in spite of the fact that he was, formally, her uncle). At the ceremonies commemorating the event, new provisions were made for the support of poor children, along the lines of earlier imperial foundations. Marcus and Lucius proved popular with the people of Rome, who strongly approved of their civiliter ("lacking pomp") behaviour. The emperors permitted free speech, evidenced by the fact that the comedy writer Marullus was able to criticize them without suffering retribution. As the biographer wrote, "No one missed the lenient ways of Pius".

Marcus replaced a number of the empire's major officials. The ab epistulis Sextus Caecilius Crescens Volusianus, in charge of the imperial correspondence, was replaced with Titus Varius Clemens. Clemens was from the frontier province of Pannonia and had served in the war in Mauretania. Recently, he had served as procurator of five provinces. He was a man suited for a time of military crisis. Lucius Volusius Maecianus, Marcus's former tutor, had been prefectural governor of Egypt at Marcus's accession. Maecianus was recalled, made senator, and appointed prefect of the treasury (aerarium Saturni). He was made consul soon after. Fronto's son-in-law, Gaius Aufidius Victorinus, was appointed governor of Germania Superior.

Fronto returned to his Roman townhouse at dawn on 28 March, having left his home in Cirta as soon as news of his pupils' accession reached him. He sent a note to the imperial freedman Charilas, asking if he could call on the emperors. Fronto would later explain that he had not dared to write the emperors directly. The tutor was immensely proud of his students. Reflecting on the speech he had written on taking his consulship in 143, when he had praised the young Marcus, Fronto was ebullient: "There was then an outstanding natural ability in you; there is now perfected excellence. There was then a crop of growing corn; there is now a ripe, gathered harvest. What I was hoping for then, I have now. The hope has become a reality". Fronto called on Marcus alone; neither thought to invite Lucius.

Lucius was less esteemed by Fronto than his brother, as his interests were on a lower level. Lucius asked Fronto to adjudicate in a dispute he and his friend Calpurnius were having on the relative merits of two actors. Marcus told Fronto of his reading – Coelius and a little Cicero – and his family. His daughters were in Rome with their great-great-aunt Matidia; Marcus thought the evening air of the country was too cold for them. He asked Fronto for 'some particularly eloquent reading matter, something of your own, or Cato, or Cicero, or Sallust or Gracchus – or some poet, for I need distraction, especially in this kind of way, by reading something that will uplift and diffuse my pressing anxieties.' Marcus's early reign proceeded smoothly; he was able to give himself wholly to philosophy and the pursuit of popular affection. Soon, however, he would find he had many anxieties. It would mean the end of the felicitas temporum ('happy times') that the coinage of 161 had proclaimed.

In either autumn 161 or spring 162, the Tiber overflowed its banks, flooding much of Rome. It drowned many animals, leaving the city in famine. Marcus and Lucius gave the crisis their personal attention. In other times of famine, the emperors are said to have provided for the Italian communities out of the Roman granaries.

Fronto's letters continued through Marcus's early reign. Fronto felt that, because of Marcus's prominence and public duties, lessons were more important now than they had ever been before. He believed Marcus was 'beginning to feel the wish to be eloquent once more, in spite of having for a time lost interest in eloquence'. Fronto would again remind his pupil of the tension between his role and his philosophic pretensions: 'Suppose, Caesar, that you can attain to the wisdom of Cleanthes and Zeno, yet, against your will, not the philosopher's woolen cape'.

The early days of Marcus's reign were the happiest of Fronto's life: Marcus was beloved by the people of Rome, an excellent emperor, a fond pupil, and perhaps most importantly, as eloquent as could be wished. Marcus had displayed rhetorical skill in his speech to the senate after an earthquake at Cyzicus. It had conveyed the drama of the disaster, and the Senate had been awed: "Not more suddenly or violently was the city stirred by the earthquake than the minds of your hearers by your speech". Fronto was hugely pleased.

On his deathbed, Antoninus spoke of nothing but the state and the foreign kings who had wronged him. One of those kings, Vologases IV of Parthia, made his move in late summer or early autumn 161. Vologases entered the Kingdom of Armenia (then a Roman client state), expelled its king and installed his own – Pacorus, an Arsacid like himself. The governor of Cappadocia, the frontline in all Armenian conflicts, was Marcus Sedatius Severianus, a Gaul with much experience in military matters.

Convinced by the prophet Alexander of Abonoteichus that he could defeat the Parthians easily and win glory for himself, Severianus led a legion (perhaps the IX Hispana) into Armenia, but was trapped by the great Parthian general Chosrhoes at Elegeia, a town just beyond the Cappadocian frontiers, high up past the headwaters of the Euphrates. After Severianus made some unsuccessful efforts to engage Chosrhoes, he committed suicide, and his legion was massacred. The campaign had lasted only three days.

There was threat of war on other frontiers as well – in Britain, and in Raetia and Upper Germany, where the Chatti of the Taunus mountains had recently crossed over the limes. Marcus was unprepared. Antoninus seems to have given him no military experience; the biographer writes that Marcus spent the whole of Antoninus's twenty-three-year reign at his emperor's side and not in the provinces, where most previous emperors had spent their early careers.

More bad news arrived: the Syrian governor's army had been defeated by the Parthians, and retreated in disarray. Reinforcements were dispatched for the Parthian frontier. P. Julius Geminius Marcianus, an African senator commanding X Gemina at Vindobona (Vienna), left for Cappadocia with detachments from the Danubian legions. Three full legions were also sent east: I Minervia from Bonn in Upper Germany, II Adiutrix from Aquincum, and V Macedonica from Troesmis.

The northern frontiers were strategically weakened; frontier governors were told to avoid conflict wherever possible. M. Annius Libo, Marcus's first cousin, was sent to replace the Syrian governor. His first consulship was in 161, so he was probably in his early thirties, and as a patrician, he lacked military experience. Marcus had chosen a reliable man rather than a talented one.

Marcus took a four-day public holiday at Alsium, a resort town on the coast of Etruria. He was too anxious to relax. Writing to Fronto, he declared that he would not speak about his holiday. Fronto replied: 'What? Do I not know that you went to Alsium with the intention of devoting yourself to games, joking, and complete leisure for four whole days?' He encouraged Marcus to rest, calling on the example of his predecessors (Antoninus had enjoyed exercise in the palaestra, fishing, and comedy), going so far as to write up a fable about the gods' division of the day between morning and evening – Marcus had apparently been spending most of his evenings on judicial matters instead of at leisure. Marcus could not take Fronto's advice. 'I have duties hanging over me that can hardly be begged off', he wrote back. Marcus Aurelius put on Fronto's voice to chastise himself: ''Much good has my advice done you', you will say!' He had rested, and would rest often, but 'this devotion to duty! Who knows better than you how demanding it is!'