Joaquín Nin y Castellanos (September 29, 1879, Havana - October 24, 1949, Havana) was a Spanish-Cuban pianist and composer.
Nin studied piano with Moritz Moszkowski and composition at the Schola Cantorum (where he taught from 1906 to 1908). He toured as a pianist and was known as a composer and arranger of popular Spanish folk music. Nin was a member of the Spanish Academy and the French Legion of Honor.
He was the father of Thorvald Nin, composer Joaquín Nin-Culmell, and writer Anaïs Nin with singer Rosa Culmell.
Joaquín Nin appears as one of the characters in the novel The Island of Eternal Love (Riverhead, 2008), by Cuban writer Daína Chaviano.
In her diaries and fiction, his psychoanalytically oriented writer daughter Anaïs Nin often attempts to explain her own personality and problems by recalling how her father treated her as a child. She was also close to him off and on as an adult. Her "unexpurgated" diary volume Incest: From a Journal of Love describes an adult incestuous relationship with him. He also appears in her fiction. She describes him as an egotistical Don Juan, and she imitated him at times by being a "Doña Juana".