Ascalon (Philistine: 𐤀𐤔𐤒𐤋𐤍, romanized: *ʾAšqalōn; Hebrew: אַשְׁקְלוֹן, romanized: ʾAšqəlōn; Koinē Greek: Ἀσκάλων, romanized: Askálōn; Latin: Ascalon; Arabic: عَسْقَلَان, romanized: ʿAsqalān) was an ancient Near East port city on the Mediterranean coast of the southern Levant of high historical significance, including early on as a major Philistine city, and later as a much contested stronghold during the Crusades. Its importance diminished after the Mamluks destroyed its fortifications and port in 1270 in order to prevent any future military and logistical use by the Crusaders.

Traces of settlement in the area around Ascalon exist from the 3rd millennium BC, with evidence of city fortifications emerging in the Middle Bronze Age. During the Late Bronze Age, Ashkelon was integrated into the Egyptian Empire, before becoming one of the five cities of the Philistine pentapolis following the migration of the Sea Peoples. The city was later destroyed by the Babylonians but was subsequently rebuilt.

Ascalon remained a major metropolis throughout antiquity and the early Middle Ages, before becoming a highly contested fortified foothold on the coast during the Crusades, when it became the site of two significant Crusader battles: the Battle of Ascalon in 1099, and the Siege of Ascalon in 1153. The Mamluk sultan Baybars ordered the destruction (slighting) of the city fortifications and the harbour in 1270 to prevent any further military use, though structures such as the Shrine of Husayn's Head survived. The nearby town of al-Majdal was established in the same period.

Ottoman tax records attest the existence of the village of Al-Jura adjacent to citadel walls from at least 1596. That residual settlement survived until its depopulation in 1948. The modern Israeli city of Ashkelon takes its name from the ancient city.

Ascalon has been known by many variations of the same basic name over the millennia. It is speculated that the name comes from the Northwest Semitic and possibly Canaanite root Ṯ-Q-L, meaning "to weigh", which is also the root of "Shekel".

The settlement is first mentioned in the Egyptian Execration Texts from the 18th-19th centuries BC as Asqalānu. In the Amarna letters (c. 1350 BC), there are seven letters to and from King Yidya of Ašqaluna and the Egyptian pharaoh. The Merneptah Stele (c. 1208 BC) of the 19th dynasty recounts the Pharaoh putting down a rebellion at Asqaluna. The settlement is then mentioned eleven times in the Hebrew Bible as ʾAšqəlōn.

In the Hellenistic period, Askálōn emerged as the Ancient Greek name for the city, persisting through the Roman period and later Byzantine period.

In the Early Islamic period, the Arabic form became ʿAsqalān. The medieval Crusaders called it Ascalon.

In modern Hebrew it is known as Ashkelon. Today, Ascalon is a designated archaeological area known as Tel Ashkelon ("Mound of Ascalon") and administered as Ashkelon National Park.

Ascalon lies on the Mediterranean coast, 16 km. north of Gaza City and 14 km. south of Ashdod and Ashdod-Yam. Around 15 million years ago, a river flowed from inland to the sea here. It was later covered by fossilized sandstone ridges (kurkar), formed by sand that was washed to the shores from the Nile Delta. The river became an underground water source, which was later exploited by Ascalon's residents for the constructions of wells. The oldest well found at Ascalon dates around 1000 BCE.

The remains of prehistoric activity and settlement at Ashkelon were revealed in salvage excavations prior to urban development in the Afridar and Marina neighborhoods of modern Ashkelon, some 1.5 kilometres (1 mi) north of Tel Ashkelon. The fieldwork was conducted in the 1950s under the supervision of Jean Perrot and in 1997-1998 under the supervision of Yosef Garfinkel.

The earliest traces of human activity include some 460 microlithic tools dated to the Epipalaeolithic period (c. 23,000 to c. 10,000 BCE). These come along wide evidence for hunter-gatherer exploitation in the southern coastal plain in that time. This activity come to hiatus during the early periods of sedentation in the Levant, and resumed only during the pre-pottery C phase of the Neolithic (c. 7000–6400 BCE). Jean Perrot's excavation revealed eight dwelling pits, along with silos and installations, while Garfinkel's excavations revealed numerous pits, hearths and animal bones.

During the Early Bronze Age I period (EB I, 3700–2900 BCE), human settlement thrived in Ashkelon. The central site was in Afridar, situated between two long and wide kurkar ridges. This area had unique ecological conditions, offering an abundance of goundwater, fertile soils and varied flora and fauna. Two other settlements existed at Tel Ashkelon itself, and in the Barnea neighborhood of modern Ashkelon. The site of Afridar is one of the most extensive and most excavated settlements of the EB I period, with over two dozen dig sites, excavated by the Israel Antiquities Authority (IAA). The flourishment of EB I Ashkelon has also been linked to trade relations with Prehistoric Egypt. The site of Afridar was abandoned at the start of the EB II period (c. 2900 BCE). It was suggested that the cause for the abandonment was a climate change causing increased precipitation, which destroyed the ecological condition that had served the locals for centuries.

In the EB II-III (2900–2500 BCE), the site of Tel Ashkelon served as an important seaport for the trade route between the Old Kingdom of Egypt and Byblos. Excavations at the northern side of the mound revealed a mudbrick structure and numerous olive-oil jars. This port was abandoned with the deurbanization of Canaan during the second half of the 3rd millennium BC (Intermediate Bronze Age). At that time, the center of settlement moved to the unwalled rural settlement at Barne'a.

Ashkelon was resettled in the Middle Bronze Age on the background of country-wide urban renaissance, linked to the immigration of Amorites people from the north, as well as the revival of trade relations between Middle Kingdom of Egypt and Byblos. It soon become the fortified center of a city-kingdom, as evidenced by both historical records and archaeology. Ashkelon first mention in historical records is in the Egyptian Execration Texts from the time of the Twelfth Dynasty of Egypt (20th–19th centuries BCE). These texts were written on red pots, which were broken as part of a cursing ritual against Egypt's enemies. Ashkelon appears three times under the name Asqanu (ꜥIsqꜥnw), along with three of its rulers ḫꜥykm (or Khalu-Kim), ḫkṯnw and Isinw. These names of Northwest Semitic origin, are identified as Amorites. Scholars have suggested Ashkelon was one of many Levantine city-states established by Amorites in the early second millennium BCE.

The most distinctive feature of the site of Ashkelon is its fortifications, consisting of free-standing earthen ramparts which were erected as early as around 1800 BCE. In the excavations of the northern slope of the ramparts, archaeologists detected five phases of construction including city gates, moats, guard towers and in a later phase, a sanctury right after the entrance to the city. The material culture and especially Egyptian-style pottery showed that Middle Bronze Ashkelon lasted until around 1560 BCE.

Ashkelon came under the control of the New Kingdom of Egypt in the time of Thutmose III, following the Battle of Megiddo (1457 BCE). During the Late Bronze Age, its territory stretched across the coastal plain, bordering Gaza to the south, Lachish and Gezer to the east and Gezer to the north.

The ties between Ashkelon and Egypt in the late 15h century are documented in Papyrus Hermitage 1116A, which is dated to the time of Amenhotep II (1427–1401 BCE). It includes list compiled by an Egyptian official detailing rations of breed and beer, that were provided to envoys of noble chariot warriors (Maryannu) from 12 Canaanite cities, including Ashkelon. It is believed that these envoys were securing the caravans that carried tribute to the Egyptian king, and that they served as his loyal ambassadors.

During the Amarna Period (mid-14th century BCE, mostly during the reign of Akhenaten), Ashkelon maintained its ties to Egypt. Over a dozen letters inscribed in clay that were found in the Amarna letters are linked to Ashkelon. A petrographic analysis of the clay used in five letters sent by a ruler named Shubandu have supported the hypothesis that he ruled Ashkelon.

After Shubandu, Ashkelon was ruled by Yidya. Seven of his letters were identified (letters no. 320–326, 370). In these he expressed his loyalty to the king and assured he will provision the Egyptian troops with bread, beer, oil, grain and cattle. In another letter sent to the king (no. 287) Abdi-Heba, the ruler of Jerusalem, accuses Yidya, as well as the rulers of Lachish and Gezer of provisioning the ʿApiru, who were adversaries of the Egyptian empire. In another letter, Yidya is asked to send glass ingots to Egypt.

The Merneptah Stele from c. 1208 BCE, commemorates the victory of Merneptah against the rebellious Ashkelon, Gezer, Yenoam and the Israelites".

The founding of Philistine Ashkelon, on top of the Egyptian-ruled Canaanite city, was dated by the site's excavators to c. 1170 BCE. Their earliest pottery, types of structures and inscriptions are similar to the early Greek urbanised centre at Mycenae in mainland Greece, adding evidence to the conclusion that they were one of the "Sea Peoples" that upset cultures throughout the Eastern Mediterranean at that time. In this period, the Hebrew Bible presents Ashkelon as one of the five Philistine cities that are constantly warring with the Israelites.

The Onomasticon of Amenope, dated to the early 11th century BCE, mentioned Ashkelon along with Gaza and Ashdod as cities of the Philistines.

In 2012, an Iron Age IIA Philistine cemetery was discovered outside the city. In 2013, 200 of the cemetery's estimated 1,200 graves were excavated. Seven were stone-built tombs. One ostracon and 18 jar handles were found to be inscribed with the Cypro-Minoan script. The ostracon was of local material and dated to 12th to 11th century BC. Five of the jar handles were manufactured in coastal Lebanon, two in Cyprus, and one locally. Fifteen of the handles were found in an Iron I context and the rest in Late Bronze Age context.

By 734 BCE, Ashkelon was captured by the Neo-Assyrian Empire, under the reign of Tiglath-Pileser III. Following the Assyrian campaign, Ashkelon, along with other southern Levantine kingdoms, paid tribute to Assyria, and thus became a vassal kingdom. A year later, while the Assyrians were preoccupied fighting Damascus, king Mitinti I of Ashkelon joined Israel, Tyre and Arab tribes in a revolt against Assyrian hegemony. The revolt failed and Mitinti I was killed and replaced by Rukibtu. The identity of Rukibtu is unknown. It has been conjectured that he was the son of Mitinti I. Otherwise it was suggested that he was a usurper, either one who was installed by the Assyrians, or one who usurped the throne on his own behalf, and secured his rule through accepting Assyrian subjugation. Either way, after Rukibu's ascension, Ashkelon resumed paying annual tributes to Assyria.

Somewhere towards the end of the 8th century BCE, Sidqa userped the throne, and joined the rebellion instigated by king Hezekiah of Judah, along with other Levantine kings. Together, they deposed king Padi of Ekron who remained loyal to Assyria. The rebellion, which was launched shortly after Sennacherib's was suppressed during his third campaign In 701 BCE, as described in the Taylor Prism. At that time, Ashkelon controlled several cities in the Yarkon River basin (near modern Tel Aviv, including Beth Dagon, Jaffa, Beneberak and Azor). These were seized and sacked during the Assyrian campaign. Sidqa himself was exiled with all of his family and was replaced Šarru-lu-dari, the son of Rukibtu, who resumed paying tribute to Assyria. During most of the 7th century BCE, Ashkelon was ruled by Mitinti II, the son of Sidqa, who was a vassal to Esarhaddon and Ashurbanipal.

Close connections between Ashkelon and Egypt developed in the days of pharaoh Psamtik I, after Egypt filled the power vacuum due to the withdrawal of the Assyrian empire from the West. This is demonstrated by the discovery of multiple Egyptian trade items, such as barrel-jars and tripods made of Nile clay, a jewelry box made of abalone shell together with a necklace of amulets. Egyptian cultic and votive items, statuettes and offering tables were likewise discovered, demonstrating a religious influence as well. According to Herodotus (c.484–c.425 BC), the city's temple of Aphrodite (Derketo) was the oldest of its kind, imitated even in Cyprus, and he mentions that this temple was pillaged by marauding Scythians during the time of their sway over the Medes (653–625 BCE).

By the end of the 7th century BCE, Ashkelon's populated is estimated to have been 10,000–12,000. It had fortifications which integrated and developed the Canaanite ramparts, in addition to an estimated 50 protective towers. Industry in included wine and olive oil production and export and possibly textile weaving. Together with Ashdod, it is the site most abundant with Red-Slipped ware, both imported and locally made, which decreases greatly further inland. Imports further included amphorae, elegant bowls and cups, "Samaria ware", and red and cream polished tableware from Phoenicia, together with amphorae and decorated fine-ware from Ionia, Corinth, Cyprus and the Greek islands.

The history of Philistine Ashkelon came to an end when the last of the Philistine cities to hold out against Babylonian king Nebuchadnezzar II. By the month of Kislev 604 BCE, the city was burnt, destroyed and its king Aga' taken into exile. Its destruction came one year after the Assyrian-Egyptian defeat in the battle of Carchemish. Concern over the strong Egyptian influence on Ashkelon, and possibly its direct rule, are possbibly what brought Nebuchadnezzar II to reduce Ashkelon to rubble, ahead of the failed Babylonian invasion of Egypt. With the Babylonian destruction, the Philistine era was over. After its destruction, Ashkelon remained desolate for seventy years, until the Persian period.

Following the Babylonian destruction, Ashkelon was deserted for about 80 years. Shortly after the Achaemenid Empire took over, Ashkelon was rebuilt around 520–510 BCE (based on ceramic evidence). It was one of the first coastal sites to be established the by Phoenicians, and in Ashkelon's case, by Tyre. The Periplus of Pseudo-Scylax from the mid-4th century, the final decades of the Achaemenid rule, calls it "Ashkelon, the city of Tyre's people". Many inscriptions in the Phoenician language were found across the site, including ostraca bearing Phoenician names from the late 6th to late 4th centuries BCE, and one East Greek vase with the Phoenician word for "cake" inscribed on it. The cult of the goddess Tanit was present at Ashkelon by that period. The city minted its own coins, with the abbreviation Aleph-Nun referring to its name.

The archaeological excavations revealed remains of the Achaemenid (Persian) period in three main locations (Grids 38, 50 and 57). The city features monumental structures constructed of ashlar stone foundations and mudbrick superstructures. It had a city plan of streets with workshops and large warehouses by the shore. In these warehouses, many imported vessels and raw materials from the Mediterranean Sea and Ancient Near East were discovered. The origin of these imports is primarily Phoenicia and the Greek regions of Attica, Corinth and Magna Graecia, as well as Cyprus, Egypt and Mesopotamia. Among those findings are luxury items such as aryballoi, black-figure and red-figure pottery, Ionian cups, athenian owl cups and a figurine of the ancient Egyptian god Osiris, made of bronze. These were dated to the entire span of the period and attest to Ashkelon's role as a major sea port.

A unique discovery in the archaeology of Ashkelon is the large dog cemetery, located within a prime location in the center of the city. Archaeologists excavated over 800 dog burials, dated between early 5th and late 4th centuries BCE. It was suggested that the inhabitants of Ashkelon viewed the dogs as sacred animals. The dogs were given special treatment in their burial, with each being interred in a shallow pit and their bones were always found in the same position. The dogs of the Canaan Dog breed, were both male and female, the majority were puppies but also matures. It is evident they died of natural causes, without human intervention or epidemic. Dogs played a role in Phoenician society and religion in that time.

Archaeological investigation showed that the city was violently destroyed by fire around 290 BCE, some decades after the conquest of the region by Alexander the Great. This destruction took place during the reign of Ptolemy I Soter, when the Ptolemaic Kingdom consolidated its rule over the Levant. Evidence of this destruction was found in all excavation areas. The structures were found collapsed and burnt. Two hoards of silver coins were found in the destruction layers, one of them apparently buried by one of the inhabitants prior to the destruction.

It had mostly friendly relations with the Hasmonean kingdom and the Herodian kingdom of Judea, in the 2nd and 1st centuries BCE. In a significant case of an early witch-hunt, during the reign of the Hasmonean queen Salome Alexandra, the court of Simeon ben Shetach sentenced to death eighty women in Ashkelon who had been charged with sorcery.

Herod the Great, who became a client king of the Roman Empire, ruling over Judea and its environs in 30 BCE, had not received Ashkelon, yet he built monumental buildings there: bath houses, elaborate fountains and large colonnades. A discredited tradition suggests Ashkelon was his birthplace. In 6 CE, when a Roman imperial province was set in Judea, overseen by a lower-rank governor, Ashkelon was moved directly to the higher jurisdiction of the governor of Syria province.

Roman era fortifications, faced with stone, followed the same footprint as the earlier Canaanite settlement, forming a vast semicircle protecting the settlement on the land side. On the sea it was defended by a high natural bluff. A roadway more than six metres (20 ft) in width ascended the rampart from the harbor and entered a gate at the top.

The city remained loyal to Rome during the Great Revolt, 66–70 CE.

The city of Ascalon appears on a fragment of the 6th-century Madaba Map.

The bishops of Ascalon whose names are known include Sabinus, who was at the First Council of Nicaea in 325, and his immediate successor, Epiphanius. Auxentius took part in the First Council of Constantinople in 381, Jobinus in a synod held in Lydda in 415, Leontius in both the Robber Council of Ephesus in 449 and the Council of Chalcedon in 451. Bishop Dionysius, who represented Ascalon at a synod in Jerusalem in 536, was on another occasion called upon to pronounce on the validity of a baptism with sand in waterless desert. He sent the person to be baptized in water.

No longer a residential bishopric, Ascalon is today listed by the Catholic Church as a titular see.

The Muslim conquest of Palestine started in 634. Islamic historian Al-Baladhuri recounts that Ascalon (ʿAsḳalân in Arabic) was one of the last Byzantine cities in the region to fall. It may have been temporarily occupied by Amr ibn al-As, but definitively surrendered after a siege to Mu'awiya I (who later founded the Umayyad Caliphate) not long after he captured the Byzantine district capital of Caesarea in c. 640. Mu'awiya turned the town into a fortified garrison, settling cavalry there. During 'Umar's and 'Uthman's rule (634–644 and 644–656, respectively), tracts of land in Ascalon were awarded to Muslims.

During the Muslim civil war of 680–692 (Second Fitna), the south of Syria came under the military rule of Abd Allah ibn al-Zubayr's caliphate. By that time, the Byzantines reoccupied Asqalan, razed the city and deported its inhabitants. While in the time of Marwan I the region came back to Umayyad hands, the Byzantines either left Ascalon or were forced out only after Marwan's son, Abd al-Malik (r. 685–705) won the civil war. Ascalon enjoyed an era of prosperity after Abd al-Malik rebuilt and fortified it. Despite it not being a good harbor, the city enjoyed its position between Syria and Egypt and their fertile lands. Islamic scholar Yaqut al-Hamawi called it "the Bride of Syria". From the year 712 Ascalon began minting its own copper coins, with the Arabic inscription "Struck in Filastin, Askalan". A son of Caliph Sulayman (r. 715–717), whose family resided in Palestine, was buried in the city.

During the Abbasid period, the power center of the caliphate shifted from Syria to Iraq. An inscription found by Charles Clermont-Ganneau in the 19th century indicates that the Abbasid caliph al-Mahdi ordered the construction of a mosque with a minaret in Asqalan in 772. Towards the end of the 9th century Abbasid rule in Syria dwindled. By 878 it was effectively under the rule of the Tulunids of Egypt, who developed the coastal cities such as Acre, Caesarea Maritima and probably also Ascalon.

In 969, the Fatimid general Jawhar captured Syria and Palestine and annexed the territory to the Fatimid Caliphate of North Africa. Ascalon prospered during the ensuing period. Islamic geographer Al-Maqdisi (945 – 991) described Ascalon, admiring its fortifications, garrison, mosque and fruits, but also recounted that its port was unsafe. A similar description was given by Persian scholar Nasir Khusraw who visited Palestine in 1047. The absence of a port was recounted also by later scholars such as Izz al-Din ibn Shaddad (1217–1285) and Abulfeda (1273 – 1331). It was cited as one of the reason why Ascalon was one of the last coastal cities to stand against the Crusaders. In the 1070s, along with a few other coastal towns in Palestine, it remained in Fatimid hands when most of Syria was conquered by the Seljuks. Fatimid rule over Ascalon was nevertheless loosened, with the governor often exercising a greater latitude of authority over the city than the nominal authority of the Egyptian caliphate.

In 1091, a couple of years after a campaign by grand vizier Badr al-Jamali to reestablish Fatimid control over the region, the head of Husayn ibn Ali (a grandson of the Islamic prophet Muhammad) was "rediscovered", prompting Badr to order the construction of a new mosque and mashhad (shrine or mausoleum) to hold the relic, known as the Shrine of Husayn's Head. According to another source, the shrine was built in 1098 by the Fatimid vizier al-Afdal Shahanshah.

During the Crusades, Ascalon was an important city due to its location near the coast and between the Crusader States and Egypt. It remained the last major Fatimid stronghold for over half a century.

Negotiations over Jerusalem between the crusaders and the Fatimids, who had recently gained control of the city from the Seljuks, broke down in May 1099 during the final stages of the First Crusade. This led to the siege and eventual capture of Jerusalem on 15 July. The remnants of the Fatimid army retreated to Ascalon. After negotiations ended in May, the Fatimids had begun raising an army at Ascalon, ready to raise the siege of Jerusalem. In August, an army of about 10,000 crusaders marched on Ascalon to meet the army being raised. They surprised the Fatimids in battle on 12 August just north of the city of Ascalon. While the crusader army defeated the Fatimid force of around 20,000, the city itself was not captured and remained in Fatimid hands, serving as a base for military activity against the Kingdom of Jerusalem. After the Crusader conquest of Jerusalem in 1099, the six elders of the Karaite Jewish community in Ascalon contributed to the ransoming of captured Jews and holy relics from Jerusalem's new rulers. The Letter of the Karaite elders of Ascalon, which was sent to the Jewish elders of Alexandria, describes their participation in the ransom effort and the ordeals suffered by many of the freed captives.

In 1100, Ascalon was among the Fatimid coastal cities (along with Arsuf, Caesarea and Acre) that paid tribute to the crusaders, as part of a short truce. In 1101, Caesarea and Arsuf were captured by the Crusaders, and their people fled to Ascalon. To protect the influx of Islamic population, military reinforcements were sent from Egypt, who provided the city with supplies and maintained its garrison. Ascalon thus became a major Fatimid frontier post. It was subjected to a Crusader blockade, often blocking the land route from Egypt, making it only accessible through the sea. The trade between Ascalon and Crusader Jerusalem resumed by that time, though the inhabitants of Ascalon regularly struggled with shortages in food and supplies. This necessitated the provisions from Egypt on several occasions each year. According to William of Tyre, the entire civilian population of the city was included in the Fatimid army registers. Fatimid ruler Al-Hafiz dispatched between 300 and 600 horesmen to protect Ascalon. Each company had 100 troops and was commanded by an Emir. A general was put in charge of all companies. They were paid 100 dinars for each emir, and 30 dinars for every horsemen. The Fatimids then used it to launch raids into the Kingdom of Jerusalem.

In July 1101, two years after the battle of Ascalon, Fatimid vizier Al-Afdal Shahanshah launched an offensive from Ascalon to recapture Jaffa. By 7 September, Baldwin I defeated the Fatimid troops, and a year later besieged the city, destroying its rural hinterlands. Ascalon was further isolated by the fall of Acre in 1104, but kept serving as a Fatimid base. In August 1105, Al-Afdal launched yet another failed attack from Ascalon, the most serious of his campaigns using both naval and ground forces. The Franks won the land battle and it has been recounted that when they encountered the Fatimid fleet in Jaffa, they threw the head of the defeated governor of Ascalon on board of the Egyptian ships, to inform them of the Crusader victory.

After the Fatimid defeat in 1105, they no longer posed immediate threat to the Crusaders. And yet, Ascalon was deemed impregnable, and its proximities to Egyptian ports made it a primary concern for their Crusader army, as it continued to serve from time to time as base for small-scale incursions. In 1124 Tyre fell to the Crusaders, making Ascalon the last Fatimid stronghold on the Levantine coast. Baldwin II of Jerusalem led an attack against Ascalon in 1125, that repelled by the Muslims, who continued their incursions. In 1134, the Crusader count of Jaffa, Hugh II, rebelled against King Fulk, who accused him of conspiring against his realm, and of intimate relations with his wife. Hugh II rode to Ascalon to seek help, and the Muslim troops were happy to contribute to the internal feud among the Crusader. Troops left Ascalon to Jaffa and raided the Sharon plain, until Fulk's forces repelled them. Later. A year later, Fatimid vizier Ridwan ibn Walakhshi was appointed governor of Ascalon and the western Nile Delta. Ridwan found refuge in Ascalon during his conflict with Bahram al-Armani in 1138–9.

In the time of Fulk, three fortresses were erected around the city, in order to address the threats it imposed on Jerusalem: Beth Gibelin (1135–6), Ibelin (1140) and Blanchgard (1142). The failure of the Second Crusade and the rise of the Zengid dynasty in Syria motivated Baldwin III of Jerusalem in 1150 to begin preparations to capture Ascalon once and for all. He fortified Gaza, which concerned the Fatimids in Egypt, who requested a pre-emptive strike by the Zengids from the north. These refused, but sent Zengid prince Usama ibn Munqidh, who stayed there for four months and helped reinforce Ascalon's fortifications.

In January 1153, crusader king Baldwin III recruited almost all land and naval forces at disposal and laid siege to Ascalon. The siege lasted seven months, during which the city was bombarded by Crusader siege weapons. The Franks found a well prepared city, with strong walls and ample supply of provisions. The Fatimids manage to send over seventy ships with resources to the city during the siege. In his recount of the conquest of Ascalon, William of Tyre described the city from the Crusader point of view:

The whole city lies in a kind of basin which is tilted down toward the sea. It is girded round with artificial mounds on which are walls, studded with towers. It is solidly fashioned and its stones are held together by cement which is as hard as stone. The walls are of a proper thickness and as high as is proportionally fitting. Even the outer fortifications which circle around the city are constructed with the same solidity and are diligently fortified. There are no springs within the circuit of the walls nor are there any nearby, but wells both outside and within the city supply an abundance of delicious drinking water. As a further precaution the citizens have built within the city several cisterns to collect rain water. There are four gates in the circuit of the walls. These are most carefully fortified with high, solid towers.

— William of Tyre, History of Deeds Done Beyond the Sea: XVII, 22-25

Much to the disadvantage of the Muslim garrison in Ascalon, internal conflicts within the Fatimid court and military led to the assassination of Fatimid vizier and general Al-Adil ibn al-Sallar, while preparing the Fatimid fleet for a counterattack. His stepson Abbas ibn Abi al-Futuh who was involved in his murder then went back to Egypt to be appointed a vizier in his stead, leaving Ascalon without his troops. In July 1153, six months after the start of the siege, there was a breach in the wall followed by a failed attack by the Templars. By that point the siege was almost abandoned, but Raymond du Puy convinced the king to resume. On 19 August, Ascalon's anchorage was taken and its defenders were subdued by the Crusaders. Ibn al-Qalanisi recorded that upon the city's surrender, all Muslims with the means to do so emigrated from the city. The Fatimids secured the head of Husayn from its mausoleum outside the city and transported it to their capital Cairo. A year after the conquest, Muslim geographer Muhammad al-Idrisi described the city's markets and fortifications, but also the destrcution of its environs, caused by its siege.

Ascalon became a crusader lordship and was granted to Amalric, the count of Jaffa and Baldwin III's brother, who later succeeded him as king. Together the two formed the County of Jaffa and Ascalon, which became one of the four major seigneuries of the Kingdom of Jerusalem. The great mosque was turned into a church - the Cathedral of St. Paul and the city was turned into a diocese directly under the Patriarch of Jerusalem. Eventually a decision from Rome subordinated it to the Bishop of Bethlehem. The Fatimid dynasty continued to disintegrate due to internal conflicts and could not retake Ascalon.

Saladin, the founder of the Ayyubid dynasty which abolished the Fatimid state, marched on Ascalon by September 1187, as part of his conquest of the Crusader States following the Battle of Hattin. He took with him the crusader prisoners, King Guy of Lusignan and Templar Grand Master Gerard of Ridefort. The prisoners were promised liberty should the city surrender under their command, but the Christian troops at Ascalon did not obey their captured king's commands. The city surrendered after a brief, yet harsh battle. The Cristian population was deported to Alexandria and from there to Europe.

The Ayyubid rule of Ascalon was short-lived. In 1191, during the Third Crusade, Saladin ordered to methodically demolish the city because of its potential strategic importance to the crusaders. This is captured in an anecdote in which a reluctant Saladin is reported to have exclaimed: "Wallah, I would rather see my children perish than lose Ascalon!" The destruction of the city and the deportation of its inhabitants is well described in Islamic sources. Some Muslim scholars including Ibn al-Athir have recounted that the destruction of Ascalon was forced upon him by his emirs. A few hundred Jews, Karaites and Rabbanites, were living in Ascalon in the second half of the 12th century, but moved to Jerusalem following its destruction.

In January 1192, crusade leader King Richard the Lionheart of England, proceeded to reconstruct Ascalon's fortifications, an endeavor that lasted four months. It thus became the most formidable fortress along the Mediterranean coast. This fact hampered the negotiations between Richard and Saladin in 1192, as Saladin demanded its destruction. Eventually, peace was signed in Jaffa and the city's recently constructed fortifications were destroyed yet again by September 1192.

In 1229, following the Treaty of Jaffa, which concluded the Sixth Crusade, brought Ascalon back to Crusader hands. And yet, because of internal strife among the crusaders, the city remained in ruins until the Ayyubids made it a frontal post to their base in Gaza. In 1239, the Barons' Crusade was launched, led by Theobald I of Navarre who planned an assault on Ayyubid forces in Egypt. He encamped in the ruins of Ascalon, later abandoning it after one of his men, Henry II, disobeyed his orders and led a failed assault on Gaza. The Knights Hospitaller signed a peace agreement with the Ayyubids and Ascalon was given to the Crusaders, who were permitted to reconstruct its fortifications. The work on Ascalon's fortifications was first overseen by Theobald I until his depart to Europe. After him, it was Hugh IV, Duke of Burgundy who replaced him and ultimately, Richard of Cornwall oversaw its completion in April 1241, again becoming one of the strongest strongholds in the Mediterranean, with a double wall and series of towers. In a letter, Richard described Ascalon as the "key" to both land and sea, and as a permanent threat to Egypt.

During Sultan As-Salih Ayyub's conflict against the crusaders, he exploited crusader defeats in Jerusalem to march on Ascalon. In 1244, the Egyptian army headed by Baybars, defeated the Hospitaller troops at Gaza and blockaded Ascalon. The city's garrison managed to hold against the Egyptian troops. In June 1247, after capturing Damascus, the Egyptians dedicated all of the military efforts to Ascalon, and the city fell on 15 October 1247, after an assault headed by Fakhr al-Din ibn al-Shaykh. Afterwards, As-Salih Ayyub ordered again the dismantling of the walls.

The ancient and medieval history of Ascalon was brought to an end in 1270, when the then Mamluk sultan Baybars ordered the citadel and harbour at the site to be destroyed as part of a wider decision to destroy the Levantine coastal towns in order to forestall future Crusader invasions. Some monuments, like the shrine of Sittna Khadra and Shrine of Husayn's Head survived. This event irreversibly changed the settlement patterns in the region. As a substitute for ‘Asqalān, Baybars established Majdal ‘Asqalān, 3 km inland, and endowed it with a magnificent Friday Mosque, a marketplace and religious shrines.

In the first Ottoman tax register of 1526/7 Ascalon (still referred to as Asqalān) and its surrounding environs were recorded as being unpopulated. By 1596 CE, the village of village of Al-Jura, then named as Jawrat al-Hajja, was founded just outside the northeastern perimeter of Ascalon's still mounded ramparts.

Beginning in the 18th century, the site was visited, and occasionally drawn, by a number of adventurers and tourists. It was also often scavenged for building materials. The first known excavation occurred in 1815. Lady Hester Stanhope dug there for two weeks using 150 workers. No real records were kept. In the 1800s some classical pieces from Ascalon (though long thought to be from Thessaloniki) were sent to the Ottoman Museum. By the time of the commissioning of the PEF Survey of Palestine in 1871–77, the interior of Ascalon's ruined perimeter was divided into cultivated fields, interspersed with wells. From 1920 to 1922 John Garstang and W. J. Phythian-Adams excavated on behalf of the Palestine Exploration Fund. They focused on two areas, one Roman and the other Philistine/Canaanite. Over the more recent decades a number of salvage excavations were carried out by the Israel Antiquities Authority.

Modern excavation began in 1985 with the Leon Levy Expedition. Between then and 2006, seventeen seasons of work took place, led by Lawrence Stager of Harvard University. In 1991 the ruins of a small ceramic tabernacle was found, containing a finely cast bronze statuette of a bull calf, originally silvered, ten centimetres (4 in) long. In the 1997 season a cuneiform table fragment was found, being a lexical list containing both Sumerian and Canaanite language columns. It was found in a Late Bronze Age II context, about 13th century BC.

William Albright said of the city: "Ascalon is a name to conjure with. Few cities in the Old World had a more romantic history than this, from the time when its fleets according to Greek tradition, held the thalassocracy of the eastern Mediterranean to its romantic destruction by its own suzerain, Saladin, who thus avoided its impending capture by the Lion Heart."

The scallion and shallot are both types of onion named after ancient Ascalon. The name "scallion" is derived from the Old French escaloigne, by way of the Vulgar Latin escalonia, from the Latin Ascalōnia caepa or onion of Ascalon. "Shallot" is also derived from escaloigne, but by way of the 1660s diminutive form eschalotte.

The derivative "Im schwarzen Walfisch zu Askalon" (In the Black Whale of Ascalon) is a German commercium song historically sung in German universities. Joseph Victor von Scheffel provided the lyrics under the title Altassyrisch (Old Assyrian) in 1854, while the melody is from 1783 or earlier.

Chronologically by death year:

• Antiochus of Ascalon (125 – 68 BC), Platonic philosopher
• Artemidorus of Ascalon (d. 46 BCE), Hellenistic philosopher
• Aristus of Ascalon (c. 120/110 – 46/45 BC), Hellenistic philosopher, brother of Antiochus
• Eutocius of Ascalon (c. 480s – c. 520s), Byzantine philosopher
• Al-Hafiz (c. 1045 – 1149), Fatimid caliph