Ashdod-Yam and its inland counterpart, Ashdod or Azotus Mesogaios, were for most of their history two closely connected but distinct entities.

[2][3] During the Crusades, as property of the lord of Ramla, Hugh, it was bequeathed to the knight Nicolas de Beroard and became known as "Castellum Beroart".

[2] Its contemporary Arabic name is "Minat al-Qal'a", after the Umayyad-era fort that was built at the site and whose ruins remain partially intact to this day.

[6] When general Pompey restored to Ashdod its independence previously lost to the Hasmonean king John Hyrcanus, the city consisted of two twin towns, the regional center of Azotos Mesogeios or A. Hippenos (lit.

"coastal Ashdod"; also written A. Paralus, Paralius) [7] The town, under its Greek designation, appears in the Madaba Map of the 6th century.

[6][8] Remains from Azotos Paralios of the Byzantine period, including a 1.500-year-old Greek dedication to a large church, were found over 2 km north of the inland Iron Age site.

A chancel screen from a synagogue from the 6th century CE testifies to the existence of a Jewish community at Ashdod-Yam during the Byzantine period.

[15][16][17] In 2021 excavations at the site of a Byzantine-era Christian basilica revealed "splendid" mosaics and tombs dug beneath the floors.

[18] In the Umayyad period, the Caliph Abd al-Malik, the builder of the Dome of the Rock, constructed a fort at Azotus Paralios in the 7th century as part of a series of coastal defenses in Palestine.

The initial purpose was to hold off the strong Byzantine navy and it constituted one link in a chain of Muslim coastal fortifications.