John, Duke of Barca

John, Duke of Barca (also John, Duke of Barcaina; Greek: Ἰωάννης ὁ Βαρκαίνης στρατηγός; d. May 640) was a Byzantine general (magister militum) and dux of the Libyan Pentapolis who died defending Egypt during the Arab conquest. There are a few mentions of him in ancient sources, but whether they all refer to the same person or not is debated.