Gelasius of Caesarea (Greek: Γελάσιος Καισαρείας; died 395) was bishop of Caesarea Maritima from 367 to 373 and from 379 to his death. He was also an author, though none of his work survives.
Gelasius participated in the First Council of Constantinople in 381. He was forced to surrender his position as bishop to the semi-Arianist Euzoius of Caesarea between the years of 373 and 379, because in matters of Christology he was a staunch Nicaean.
In Christian tradition, the True Cross is the original wooden cross on which Jesus of Nazareth was crucified.
It is related by numerous historical accounts and legends that Helen, the mother of Roman emperor Constantine the Great, recovered the True Cross at the Holy Sepulchre in Jerusalem, when she travelled to the Holy Land in the years 326–328. The late fourth-century historians Gelasius of Caesarea and Tyrannius Rufinus wrote that while Helen was there, she discovered the hiding place of three crosses that were believed to have been used at the crucifixion of Jesus and the two thieves, Dismas and Gestas, who were executed with him. To one cross was affixed the titulus bearing Jesus' name, but according to Rufinus, Helen was unsure of its legitimacy until a miracle revealed that it was the True Cross. This event is celebrated on the liturgical calendar as the Feast of the Exaltation of the Cross (Roodmas) by the Oriental Orthodox, Eastern Orthodox, Persian, Roman Catholic, Lutheran, and Anglican churches.