The Samar Island Natural Park, in Samar, is the largest contiguous tract of old-growth forest in the Philippines. It is the country's largest terrestrial protected area, with an area of. The buffer is spread north to south over the island's three provinces and totals, about a third of the entire island of Samar. The park includes some of the island's well-known natural landmarks and landscapes which have been earlier designated for protection, namely the former Sohoton Natural Bridge National Park, the former Calbiga Caves Protected Landscape, the former Taft Forest Wildlife Sanctuary, the former Jicontol Watershed Forest Reserve and the former Bulosao Watershed Forest Reserve. It has a large biodiversity. It is a center of plant and animal diversity and endemism in the Philippines containing a remarkable number of threatened species belonging to the Eastern Visayas and Mindanao biogeographic region.
The Sohoton Natural Bridge Park is a conservation area and ecotourism site in the municipality of Basey known for its outstanding geological features including its natural stone bridge which connects two mountain ridges across a gorge, and an extensive cave system with unique limestone formations. It covers and was earlier established on July 19, 1935, through Proclamation No. 831 issued by Governor-GeneralFrank Murphy.
Calbiga Caves Park
The Langun-Gobingob cave system is within the natural park. It is considered the biggest cave in the Philippines.
Taft Forest
In the municipality of Taft, Eastern Samar, of rainforest have been protected as a wildlife sanctuary since 1999. The area is a known nesting site and natural habitat of the critically endangered Philippine eagle. The endemic giant forest raptor was first spotted in the island in the municipality of Paranas on June 15, 1856, by the British explorer John Whitehead.
Jicontol Forest
The Jicontol Watershed Forest Reserve, first gazetted in 1992 and reclassified as a natural park in 1998, covers in the municipalities of Dolores, Can-avid and Maslog. It is a component of the Mounts Cabalantian–Capotoan Complex, an important bird area, which comprises the mountains of central Samar at the border of Eastern Samar and Samar provinces. This forest is home to many threatened and restricted-range species of the Mindanao and Eastern Visayas Endemic Bird Area, such as the Samar hornbill, Visayan broadbill and yellow-breasted tailorbird. Its forest cover consists of typical dipterocarp and molave-dipterocarp with mid mountain type vegetation in the highest peaks reaching to. There have also been sightings of the Southern silvery kingfisher and the Philippine eagle within the forest.
Bulosao Watershed
The Bulosao watershed reserve in the forests of the southern Samar mountain range adjacent to the MacArthur mountains was established in 1992 to preserve and maintain the usefulness of the Bulosao River as a source of water for domestic use and irrigation of the municipalities of Marabut and Lawaan. The forest park borders the Sulat River to the north and west, and includes Mount Honop, its highest peak at.