Apo Reef is a series of coral reefs encompassing 34 square kilometers within the waters of Occidental Mindoro in the Philippines. It is the world's second-largest contiguous coral reef system and the largest in the country. The reef and its surrounding waters are administered as a National Park as part of the Apo Reef Natural Park project.

           Apo Reef can be found around 33 kilometers west off of the mid-western coast of the Philippine island of Mindoro. Two separate coral reefs make up the atoll-reef system. The two reefs are separated by a 30 meter-deep channel between them. Several environments can be found within the reef's boundaries. Aside from coral reefs, sea grass mea dows, beds of macro algae and mangrove stands are present on and around the reef proper.