Manannan mac Lir, Manannan son of the Sea, is the Irish god of the ocean and of the Otherworld, one of the most vivid and beloved figures of Irish and Manx tradition. He rides across the waves and over the land in a self-guiding boat that needs neither oar nor sail, and drives a chariot drawn by a horse, Enbarr of the flowing mane, that runs as easily over the sea as over the plain; to him the sea is a flowery, fertile plain, and its waves are his herds. He is lord of the blessed islands beyond the water, the paradisal lands of the Otherworld such as Emain Ablach, the Isle of Apples, and he moves freely between that world and this.
The Isle of Man takes its name from him, and Manx tradition remembers him as its first ruler and guardian, to whom offerings of rushes were once made. Manannan appears in some of the earliest surviving Irish literature. The ninth-century Sanas Cormaic (Cormac's Glossary), attributed to Cormac mac Cuilennain, king-bishop of Munster, already euhemerizes him as a famous historical merchant of the Isle of Man, the best sailor in western Europe, who read the weather by studying the sky, showing the god being reinterpreted as a skilled human even in an early medieval Christian-scholarly setting. In the earlier voyage-tale Immram Brain, Manannan appears riding his chariot across the waves to greet the hero Bran, identifying himself by name and foretelling the birth of his own son, Mongan, one of the oldest literary appearances of the god as a divine rather than euhemerized figure.