Fritz Reuter Leiber Jr. ( LY-bər; December 24, 1910 – September 5, 1992) was an American writer of fantasy, horror, and science fiction.
His prominent works include the sword and sorcery characters Fafhrd and the Gray Mouser featured in 36 stories and one novel, and the award-winning novels The Big Time (1958) and Our Lady of Darkness (1979). Leiber was a friend of H. P. Lovecraft, and wrote several stories in the Cthulhu Mythos.