Mariano C. del Castillo (born July 29, 1949) is a former associate justice of the Supreme Court of the Philippines. After graduating from San Beda College, Del Castillo pursued law studies at the Ateneo de Manila University. He joined the judiciary in 1989 as a Municipal Trial Court judge of San Mateo, Rizal before he was promoted as a Regional Trial Court judge of Angeles City in 1992, and later as a Regional Trial Court judge of Quezon City in 1995, where he was appointed First Vice-Executive Judge. He was appointed as a CA justice in 2001. He was active in the Philippine Judges Association, where he served as director, vice-president for administration, senior vice-president, and executive vice-president.