The name of Castellar first appeared on January 19, 1258, on an act of cession from the Count of Ventimiglia to the Count of Provence, Charles of Anjou. It originates from the Latin castellum, meaning the site of the castle. The fortress of the village, first cited in 1302, would have always been occupied by lords of the Ventimiglia-Lascaris family. Their domination over the area of Castellar started following the marriage in 1261 of Count Guillaume-Pierre of Ventimiglia with Eudoxia Lascaris, of the imperial family of Byzantium. The historic heart of the current village, consisting of 29 houses of the same height and width, was established on Saint-Sébastien hill between 1435 and 1440.