Jacob of Nisibis (, ; died c. AD 338 or 350), is an Assyrian saint. He was the second bishop of Nisibis and was called the "Moses of Mesopotamia" for his wisdom and wonderworking abilities. He was also the spiritual father of the renowned Assyrian Ephrem the Syrian, a celebrated ascetic and one of the 318 fathers of the First Ecumenical Council at Nicaea.