The wonderous man who created a world, then spent years and years expanding it, creating entire cultures, languages, mythologies, etc. His best-known works are of Middle Earth, though he did work on a few unrelated tales.
Works I remember the titles of (though there's far more than this)
The Lord of the Rings
The Hobbit
The Silmarillion
Children of Hurin
Father Christmas Letters
The Adventures of Tom Bombadil
Leaf by Niggle