Arsuf, also known as Arsur or Apollonia, is an ancient city and fortress in Outremer, on a cliff above the Mediterranean Sea.

In 640, the town was captured by Muslims. The town's area decreased, and for the first time it was surrounded by a fortified wall with buttresses, to resist the constant attacks of Byzantine fleets from the sea. Large marketplaces appeared, and a large scale pottery production center was established. In 809, following the death of Harun al-Rashid, the city fell to the Emirate of Damascus.

In 1101 Arsuf fell to a Byzantine army led by Alexios Komnenius. The Byzantines, who called it Apollonia, rebuilt the city's walls, and created the Governorship of Arsuf in the Province of Palastine. In 1187 Arsuf was captured by the Emirate of Jerusalem, but fell to the Crusaders in 1191, after a battle between Richard the Lionheart and Saladin.