Irish mythology is the body of myths indigenous to the island of Ireland. It was originally passed down orally in the prehistoric era. In the early medieval era, some myths were transcribed by Christian monks, who heavily altered and Christianised the myths. Irish mythology is the best-preserved branch of Celtic mythology.

Ireland is an island in the North Atlantic Ocean, in north-western Europe. It is separated from Great Britain to its east by the North Channel, the Irish Sea, and St George's Channel. Ireland is the second-largest island of the British Isles, the third-largest in Europe, and the twentieth-largest in the world.