Alonso de Castillo (1584?, probably in Tordesillas, Valladolid – 1647?, probably in Palermo) was a Spanish novelist and playwright. He is said to have been baptized October 1, 1584. He is next heard of at Madrid in 1619 as a man of literary tastes. While in the service of the Marquis de Villars, he issued his first work, Donaires del Parnaso (1624–1625), two volumes of humorous poems; his Tardes entretenidas (1625) and Jornadas alegres (1626) proved that he was a novelist by vocation.