Claim: Gregor Clegane is from the fictional kingdom of Westeros created by George R. R. Martin.
Evidence: Introduced in 1996 's A Game of Thrones , Gregor is the older brother of Sandor Clegane , from the fictional kingdom of Westeros.
A Game of Thrones is the first novel in A Song of Ice and Fire , a series of fantasy novels by American author George R. R. Martin.