Apo Reef is a protected marine area located in the waters of Occidental Mindoro province, Philippines. It is considered as the largest coral reef system in the country and one of the largest in the world. The reef covers an area of over 34 square kilometers and is divided into two separate reefs, the Apo Reef Natural Park and the Apo Island Reef. The park has been declared a protected area and is home to a diverse range of marine life including over 500 species of fish, sharks, manta rays, and sea turtles.

The Apo Reef Natural Park is composed of two coral atolls, the Apo Island and Apo Menor. The larger Apo Island has a lagoon at its center with a depth of up to 30 meters, while the smaller Apo Menor has a shallow lagoon. The reefs are home to a variety of coral species, including brain corals, staghorn corals, and elkhorn corals.

The Apo Reef is a popular destination for snorkeling, scuba diving, and other water activities. Visitors can explore the reef and its marine life through guided tours offered by local operators. It is also a popular site for research and scientific studies due to its rich biodiversity.

To protect the reef and its marine life, fishing and other activities that may harm the coral and marine animals are strictly regulated within the park. The reef is also a designated RAMSAR site, which means it is recognized as an important wetland and protected under international law.