Otherworld is a fictional dimension appearing in American comic books published by Marvel Comics. It is more commonly known as, and based on, the mythical Avalon from Celtic and more specifically Welsh mythology. Avalon first appeared in Fantastic Four #54 (September 1966) by Stan Lee and Jack Kirby. Avalon's dimension was referred to as Otherworld for the first time in Captain Britain #1 (October 1976) by Chris Claremont, Herb Trimpe, and Fred Kida.