|Also known as||Old Castro|
|First appearance||"The Call of Cthulhu"|
|Last appearance||"The Call of Cthulhu"|
|Created by||H. P. Lovecraft|
Castro is a fictional character created by H. P. Lovecraft, who makes his first appearance in the 1928 short story "The Call of Cthulhu". He is an "immensely aged mestizo [...] who claimed to have sailed to strange ports and talked with undying leaders of the Cthulhu Cult in the mountains of China." Castro was arrested on November 1, 1907 during a New Orleans police raid on a cult ceremony in Louisiana.
- Robert M. Price believes that Castro's name is based on that of Adolphe DeCastro–born Adolph Danziger–an author of "unbelievably bad fiction" who hired Lovecraft as a ghostwriter. Joshi and Schultz, however, report that Lovecraft did not become acquainted with DeCastro until late 1927, whereas "The Call of Cthulhu" was completed in 1926.