Gelasius is a masculine given name, from Greek (Gelásios), from Ancient Greek (gélasis, “laughing”). It may refer to:
Gelasius of Nilopolis, Egyptian Christian abbot Gelasius of Caesarea (died 395), bishop of Caesarea Pope Gelasius I (died 496) Gelasius of Cyzicus, misidentified as 5th century ecclesiastical writer Anonymus Cyzicenus Pope Gelasius II (died 1119) Gelasius, Archbishop of Armagh (died 1174) Gelasius Ó Cuileanáin (died 1580), Cistercian Abbot of Boyle, Ireland Nikollë Gazulli (1895–1946), who wrote under the pseudonym Gelasius