John IV Laskaris, Byzantine emperor (died 1305)

John IV Doukas Laskaris was the fourth emperor of the Nicaean Empire from August 16, 1258 to December 25, 1261, one of the Greek successor states formed after the Sack of Constantinople by the Roman Catholics during the Fourth Crusade. He was the last emperor from the prominent Laskarid dynasty and the last to only rule Nicaea before the Reconquest of Constantinople by his successor in 1261.