Ashkelon was the oldest and largest seaport in Ancient Israel, one of the "five cities" of the Philistines, north of Gaza and south of Jaffa (Yafa). Archaeological excavations begun in 1985 led by Lawrence Stager of Harvard University are revealing the site with about 50 feet (15 m) of accumulated rubble from successive Canaanite, Philistine, Phoenician, Iranian, Hellenistic, Roman, Byzantine, Islamic, and Crusader occupation.

In the oldest layers are shaft graves of pre-Phoenician Canaanites. The city was originally built on a sandstone outcropping and has a good underground water supply. It was relatively large as an ancient city with as many as 15,000 people living inside walls a mile and a half (2.4 km) long, 50 feet (15 m) high and 150 feet (50 m) thick. Ashkelon was a thriving Middle Bronze Age (2000-1550 BC) city of more than 150 acres (607,000 m²), with commanding ramparts including the oldestarched city gate in the world, eight feet wide, and even as a ruin still standing two stories high. The thickness of the walls was so great that the mudbrick Bronze Age gate had a stone-lined tunnel-like barrel vault, coated with white plaster, to support the superstructure: it is the oldest such vault ever found.

The Bronze Age ramparts were so capacious that later Roman and Islamic fortifications, faced with stone, followed the same footprint, a vast semi-circle protecting Ashkelon on the landward side. On the sea it was defended by a high natural bluff.

Within the huge ramparts, in the ruins of a sanctuary, a votive silver calf was found in 1991. During the Canaanite period, a roadway more than 20 feet (6.1 m) in width ascended the rampart from the harbor and entered a gate at the top. Nearby, in the ruins of a small ceramic tabernacle was found a finely cast bronze statuette of a bull calf, originally silvered, 4 inches (100 mm) long. Images of calves and bulls were associated with the worship of the Canaanite gods El and Baal.

The Amarna letters correspondence of Ashkelon/(Ašqaluna), of 1350 BC, contains seven letters to the Egyptian pharaoh, from its 'King'/mayor: Yidya. Yidya was the only ruler of Ašqaluna during the 15-20 year time period. One letter from the pharaoh to Yidya, was subsequently discovered in the early 1900s.

The Philistines conquered Canaanite Ashkelon about 1150 BC. Their earliest pottery, types of structures and inscriptions are similar to the early Greek urbanised centre atMycenae in mainland Greece, adding weight to the hypothesis that the Philistines were of Mycenaeic origin possibly one of the populations among the "Sea Peoples" that upset cultures throughout the eastern Mediterranean at that time. Ashkelon became one of the five Philistine cities that were constantly warring with the Israelitesand the kingdom of Judah. According to Herodotus, its temple of Venus 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 BC). When this vast seaport, the last of the Philistine cities to hold out againstNebuchadnezzar finally fell in 604 BC, burnt and destroyed and its people taken into exile, the Philistine era was over.

Ashkelon was soon rebuilt. It was an important Hellenistic seaport. In the period of theHasmonean Kingdom, Rabbi Simeon ben Shetach - Pharisee scholar and Nasi of theSanhedrin in the First Century B.C. - is reported to have on a single day sentenced to death eighty Ashkelon women who had been charged with witchcraft. Later, the women's relatives took revenge by bringing false witnesses against Simeon's son and causing him to be executed in turn.^{[citation needed]}

Ashkelon may have been the birthplace of Herod the Great. Josephus makes it clear that Ashkelon was not ceded to Herod the Great in 30 BC (War 1.396; Ant. 15.217), yet he built monumental buildings there: bath houses, elaborate fountains and large colonnades.^[2]

During the period of the Crusades, Ashkelon (which was known to the Crusaders asAscalon) was an important city due to its location near the coast and between theCrusader States and Egypt. In 1099, shortly after the Siege of Jerusalem (1099) an Egyptian Fatimid army which had been sent to relieve Jerusalem was defeated by a Crusader force at the Battle of Ascalon. The city itself was not captured by the Crusaders because of internal disputes amongst their leaders. This battle is widely considered to have signified the end of the First Crusade. Until 1153, the Fatimids were able to launch raids into the Kingdom of Jerusalem from Ashkelon which meant that the southern border of the Crusader States was constantly unstable. In response to these incursions into Outremer, King Fulk of Jerusalem constructed a number of Christian settlements around the city during the 1130s, in order to neutralise the threat of the Muslim garrison. In 1148, during the Second Crusade, the city was unsuccessfully besieged for eight days by a small Crusader army which was not fully supported by the Crusader States. In 1150 the Fatimids fortified the city with fifty-three towers as it was their most important frontier fortress. Three years later, after afive month siege, the city was captured by a Crusader army lead by King Baldwin III of Jerusalem. It was then added to the County of Jaffa to form the County of Jaffa and Ascalon which became one of the four major seigneuries of the Kingdom of Jerusalem. In 1187 Saladin took Ashkelon as part of his conquest of the Crusader States following the Battle of Hattin. In 1191, during the Third Crusade, Saladin demolished the city because of its potential strategic importance to the Christians, but the leader of the Crusade, King Richard I of England, constructed a citadel upon the ruins. Ashkelon subsequently remained part of the diminished territores of Outremer throughout most of the 13th century and Richard, Earl of Cornwall reconstructed and refortified the citadel during 1240-41, as part of the Crusader policy of improving the defences of coastal sites. The Egyptians regained Ashkelon in 1247 during As-Salih Ayyub's conflict with the Crusader States and the city was returned to Muslim rule. The Mamluk dynasty came into power in Egypt in 1250 and the ancient and medieval history of Ashkelon was brought to an end in 1270, when the Mamluk sultan Baybarsordered the citadel and harbour at the site to be destroyed. As a result of this destruction, the site was abandoned by its inhabitants and fell into disuse.

After the Crusader conquest of Jerusalem the six elders of the Karaite Jewish community in Ashkelon 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.