Manannán Mac Lir was the legendary sea-god of the Tuatha Dé Danann. These were the people that lived in Ireland during the Bronze Age. He also appears in lots of the Scots and Manx ( Isle of Man ) mythology.
Manannán Mac Lir is said to have been the first ruler of the Isle of Man, and the Tuatha Dé Danann believed he had a great palace and throne there.
In fact, this is where he got his name, as ‘Manand’ is the Old Irish name for the Isle of Man. As his surname suggests, he was the son of Lir. Lir, meaning ‘sea’, was a great sea-god and it seems that Manannán eventually took over that role.