Tell Umm Amer, also known as Saint Hilarion Monastery, is an ancient Christian monastery south of Gaza in the Palestinian territories. Its archaeological remains span more than four centuries and are characterized by five successive churches, bath and sanctuary complexes, geometric mosaics, and an expansive crypt. The site's oldest building, dating to the 4th century, is named for Hilarion, a native of the Gaza region and the father of Palestinian monasticism.