Mariano C. del Castillo (born July 29, 1949) is a former associate justice of the Supreme Court of the Philippines.

[1] After graduating from San Beda College, Del Castillo pursued law studies at the Ateneo de Manila University.

Likewise, he has held various positions in religious, civic, community, and non-governmental organizations.

He taught Practice Court II at the Ateneo College of Law and lectures at the Mandatory Continuing Legal Education (MCLE) and Philippine Judicial Academy (PHILJA) seminars.

On 28 April 2010, Justice del Castillo penned the decision on Vinuya vs. Executive Secretary, a case involving Filipina sex slavery victims during the Japanese occupation in the Second World War.