Which language must an author write in order to receive the Miguel de Cervantes Prize?

The Miguel de Cervantes Prize (Spanish: Premio de Literatura en Lengua Castellana Miguel de Cervantes) is awarded annually to honor the lifetime achievement of an outstanding writer in the Spanish language.

Three of the 45 winners of the Miguel de Cervantes Prize have also won the Nobel Prize in Literature. Octavio Paz (Cervantes 1981, Nobel 1990) and Mario Vargas Llosa (Cervantes 1994, Nobel 2010), were awarded the Nobel Prize in subsequent years, while Camilo José Cela received the Nobel Prize in 1989 and was awarded the Cervantes Prize in 1995.