The Temple of Artemis or Artemision (Greek: Ἀρτεμίσιον; Turkish: Artemis Tapınağı), also known as the Temple of Diana, was a Greek temple dedicated to an ancient, localised form of the goddess Artemis (equated with the Roman goddess Diana). It was located in Ephesus (near the modern town of Selçuk in present-day Turkey). By AD 401 it had been ruined or destroyed. Only foundations and fragments of the last temple remain at the site.

The earliest version of the temple (a Bronze Age temenos) antedated the Ionic immigration by many years. Callimachus, in his Hymn to Artemis, attributed it to the Amazons. In the 7th century BC, it was destroyed by a flood.

Its reconstruction, in more grandiose form, began around 550 BC, under Chersiphron, the Cretan architect, and his son Metagenes. The project was funded by Croesus of Lydia, and took 10 years to complete. This version of the temple was destroyed in 356 BC by an arsonist, commonly thought to have been a madman named Herostratus.

The next, greatest, and last form of the temple, funded by the Ephesians themselves, is described in Antipater of Sidon's list of the world's Seven Wonders:

I have set eyes on the wall of lofty Babylon on which is a road for chariots, and the statue of Zeus by the Alpheus, and the hanging gardens, and the colossus of the Sun, and the huge labour of the high pyramids, and the vast tomb of Mausolus; but when I saw the house of Artemis that mounted to the clouds, those other marvels lost their brilliancy, and I said, "Lo, apart from Olympus, the Sun never looked on aught so grand".

The Temple of Artemis (artemisia) was located near the ancient city of Ephesus, about 75 kilometres (47 mi) south from the modern port city of İzmir, in Turkey. Today the site lies on the edge of the modern town of Selçuk.

The sacred site (temenos) at Ephesus was far older than the Artemision itself. Pausanias was certain that it antedated the Ionic immigration by many years, being older even than the oracular shrine of Apollo at Didyma. He said that the pre-Ionic inhabitants of the city were Leleges and Lydians. Callimachus, in his Hymn to Artemis attributed the earliest temenos at Ephesus to the Amazons, legendary warrior-women whose religious practise he imagined already centered upon an image (bretas) of Artemis, their matron goddess. Pausanias believed that the temple pre-dated the Amazons.

Pausanias's estimation of the site's antiquity seems well-founded. Before World War I, site excavations by David George Hogarth seemed to identify three successive temple buildings. Re-excavations in 1987–1988 and re-appraisal of Hogarth's account confirmed that the site was occupied as early as the Bronze Age, with a sequence of pottery finds that extend forward to Middle Geometric times, when a peripteral temple with a floor of hard-packed clay was constructed in the second half of the 8th century BC. The peripteral temple at Ephesus offers the earliest example of a peripteral type on the coast of Asia Minor, and perhaps the earliest Greek temple surrounded by colonnades anywhere.

In the 7th century BC, a flood destroyed the temple, depositing over half a meter of sand and flotsam over the original clay floor. Among the flood debris were the remains of a carved ivory plaque of a griffin and the Tree of Life, apparently North Syrian, and some drilled tear-shaped amber drops of elliptical cross-section. These probably once dressed a wooden effigy (xoanon) of the Lady of Ephesus, which must have been destroyed or recovered from the flood. Bammer notes that though the site was prone to flooding, and raised by silt deposits about two metres between the 8th and 6th centuries, and a further 2.4 m between the sixth and the fourth, its continued use "indicates that maintaining the identity of the actual location played an important role in the sacred organization".

The new temple was sponsored at least in part by Croesus, who founded Lydia's empire and was overlord of Ephesus. It was designed and constructed from around 550 BC by the Cretan architect Chersiphron and his son Metagenes. It was 115 m (377 ft) long and 46 m (151 ft) wide, supposedly the first Greek temple built of marble. Its peripteral columns stood some 13 m (40 ft) high, in double rows that formed a wide ceremonial passage around the cella that housed the goddess's cult image. Thirty-six of these columns were, according to Pliny the Elder, decorated by carvings in relief. A new ebony or blackened grapewood cult statue was sculpted by Endoios, and a naiskos to house it was erected east of the open-air altar.

A rich foundation deposit from this era, also called the "Artemision deposit", yielded more than a thousand items, including what may be the earliest coins made from the silver-gold alloy electrum. The deposit contains some of the earliest inscribed coins, those of Phanes, dated to 625–600 BC from Ephesus, with the legend ΦΑΕΝΟΣ ΕΜΙ ΣΗΜΑ (or similar) ("I am the badge of Phanes"), or just bearing the name ΦΑΝΕΟΣ ("of Phanes").

Fragments of bas-relief on the lowest drums of the temple columns, preserved in the British Museum, show that the enriched columns of the later temple, of which a few survive (illustration below) were versions of this earlier feature. Pliny the Elder, seemingly unaware of the ancient continuity of the sacred site, claims that the new temple's architects chose to build it on marshy ground as a precaution against earthquakes, with lower foundation layers of fleeces and pounded charcoal.

The temple became an important attraction, visited by merchants, kings, and sightseers, many of whom paid homage to Artemis in the form of jewelry and various goods. It also offered sanctuary to those fleeing persecution or punishment, a tradition linked in myth to the Amazons who twice fled there seeking the goddess's protection from punishment, firstly by Dionysus and later, by Heracles. Diogenes Laertius claims that the misanthropic philosopher Heraclitus, thoroughly disapproving of civil life at Ephesus, played knucklebones in the temple with the boys, and later deposited his writings there.

In 356 BC, the temple burned down. Various sources describe this as a vainglorious act of arson by a man, Herostratus, who set fire to the wooden roof-beams, seeking fame at any cost; thus the term herostratic fame. For this outrage, the Ephesians sentenced the perpetrator to death and forbade anyone from mentioning his name, although Theopompus later noted it. Aristotle describes the temple's conflagration, but not its cause. In Greek and Roman historical tradition, the temple's destruction coincided with the birth of Alexander the Great (around 20–21 July 356 BC). Plutarch remarks that Artemis was too preoccupied with Alexander's delivery to save her burning temple; he does not specify a cause for the fire.

Herostratus' part in the temple's destruction has been questioned in modern scholarship. Stefan Karweise notes that any arsonist would have needed access to the wooden roof framing; Knibbe (1998) writes of an "entire corps" of attested temple guards and custodians. The fire might even have been deliberately and covertly set by the temple's administrators, who were aware that the temple's foundation was sinking but were prevented from re-siting it elsewhere by religious constraints; Bammer has noted the conservation of the original sacred location throughout successive rebuildings, despite continued problems with flooding and foundations. Karwiese questions the motive of Herostratus since he only divulged his purpose under torture, which does not fit a man seeking fame. Knibbe (1998) considers Herostratus a "useful idiot in the service of the priesthood".

Alexander offered to pay for the temple's rebuilding; the Ephesians tactfully refused, saying "it would be improper for one god to build a temple to another", and eventually rebuilt it after his death, at their own expense. Work started in 323 BC and continued for many years. The third temple was larger than the second; 137 m (450 ft) long by 69 m (225 ft) wide and 18 m (60 ft) high, with more than 127 columns. Athenagoras of Athens names Endoeus, a pupil of Daedalus, as sculptor of Artemis' main cult image.

Pausanias (c. 2nd century AD) reports another image and altar in the temple, dedicated to Artemis Protothronia (Artemis "of the first seat") and a gallery of images above this altar, including an ancient figure of Nyx (the primordial goddess of Night) by the sculptor Rhoecus (6th century BC). Pliny describes images of Amazons, the legendary founders of Ephesus and Ephesian Artemis' original protégés, carved by Scopas. Literary sources describe the temple's adornment by paintings, columns gilded with gold and silver, and religious works of renowned Greek sculptors Polyclitus, Pheidias, Cresilas, and Phradmon.

This reconstruction survived for 600 years and appears multiple times in early Christian accounts of Ephesus. According to the New Testament, the appearance of the first Christian missionary in Ephesus caused locals to fear for the temple's dishonor. The 2nd century Acts of John includes an apocryphal tale of the temple's destruction: The apostle John prayed publicly in the Temple of Artemis, exorcising its demons and "of a sudden the altar of Artemis split in many pieces ... and half the temple fell down," instantly converting the Ephesians, who wept, prayed, or took flight.

Against this, a Roman edict of 162 AD acknowledges the importance of Artemesion, the annual Ephesian festival to Artemis, and officially extended it from a few holy days over March–April to a whole month, "one of the largest and most magnificent religious festivals in Ephesus' liturgical calendar".

In 268 AD, according to Jordanes, a raid by the Goths, under their leaders "Respa, Veduc, and Thurar", "laid waste many populous cities and set fire to the renowned temple of Diana at Ephesus." The extent and severity of the damage are unknown; the temple may have lain derelict until its official closure during the persecution of pagans in the late Roman Empire. Ammonius of Alexandria comments on its closure, perhaps as early as 407 CE, or no later than the mid 5th century. After closure and after the city had become Christian, the name of Artemis appears to have been erased from inscriptions throughout Ephesus.

Cyril of Alexandria credited Archbishop of Constantinople John Chrysostom with destroying the temple, referring to him as "the destroyer of the demons and overthrower of the temple of Diana". A later Archbishop of Constantinople, Proclus, noted the achievements of John, saying "In Ephesus, he despoiled the art of Midas," but there is little evidence to support this claim.

At least some of the stone from the abandoned temple was used in construction of other buildings. A legend of the Late Middle Ages claims that some of the columns in the Hagia Sophia were taken from the Temple of Artemis at Ephesus, but there is no truth to this story.

The main primary sources for the Temple of Artemis at Ephesus are Pliny the Elder's Natural History, writings by Pomponius Mela, and Plutarch's Life of Alexander.

The site of the temple was rediscovered in 1869, after six years of searching by an expedition led by John Turtle Wood and sponsored by the British Museum. These excavations continued until 1874. A few further fragments of sculpture were found during the 1904–1906 excavations directed by David George Hogarth. The recovered sculptured fragments of the 4th-century rebuilding and a few from the earlier temple, which had been used in the rubble fill for the rebuilding, were assembled and displayed in the "Ephesus Room" of the British Museum. In addition, the museum has part of possibly the oldest cache of coins in the world (600 BC) that had been buried in the foundations of the Archaic temple.

Today the site of the temple, which lies just outside Selçuk, is marked by a single column constructed of miscellaneous fragments discovered at the site.

The archaic temenos beneath the later temples clearly housed some form of "Great Goddess" but nothing is known of her cult. The literary accounts that describe it as "Amazonian" refer to the later founder-myths of Greek émigrés who developed the cult and temple of Artemis Ephesia. The wealth and splendor of temple and city were taken as evidence of Artemis Ephesia's power, and were the basis for her local and international prestige: despite the successive traumas of Temple destruction, each rebuilding – a gift and honor to the goddess – brought further prosperity. Large numbers of people came to Ephesus in March and in the beginning of May to attend the main Artemis Procession.

Artemis' shrines, temples and festivals (Artemisia) could be found throughout the Greek world, but Ephesian Artemis was unique. The Ephesians considered her theirs, and resented any foreign claims to her protection. Once Persia ousted and replaced their Lydian overlord Croesus, the Ephesians played down his contribution to the temple's restoration. On the whole, the Persians dealt fairly with Ephesus, but removed some religious artifacts from Artemis' Temple to Sardis and brought Persian priests into her Ephesian cult; this was not forgiven. When Alexander conquered the Persians, his offer to finance the temple's second rebuilding was politely but firmly refused. Ephesian Artemis lent her city's diplomacy a powerful religious edge.

Under Hellenic rule, and later, under Roman rule, the Ephesian Artemisia festival was increasingly promoted as a key element in the pan-Hellenic festival circuit. It was part of a definitively Greek political and cultural identity, essential to the economic life of the region, and an excellent opportunity for young, unmarried Greeks of both sexes to seek out marriage partners. Games, contests and theatrical performances were held in the goddess's name, and Pliny describes her procession as a magnificent crowd-puller; it was shown in one of Apelles' best paintings, which depicted the goddess's image carried through the streets and surrounded by maidens. In the Roman Imperial era, the emperor Commodus lent his name to the festival games, and might have sponsored them.