This small, slimy hobbit lived on an island in the centre of an underground lake, in the story The Lord of the Rings. He was endowed with magic that extended his life well past the time when he should have left the building.
Gollum thought his staying power was due to a ring that he called My Precious. But I think his regular meals of cave fish and seaweed was the most likely reason for his amazing, long life. More