Siargao is a tear-drop shaped island in the Philippine Sea situated 800 kilometers southeast of Manila in the province of Surigao del Norte. It has a land area of approximately 437 square kilometres (169 sq mi). The east coast is relatively straight with one deep inlet, Port Pilar. The coastline is marked by a succession of reefs, small points and white, sandy beaches. The neighboring islands and islets have similar landforms.

The island is composed of municipalities of Burgos, Dapa, Del Carmen, General Luna, San Benito, Pilar, San Isidro, Santa Monica and Socorro.

Siargao Island contains the largest mangrove forest reserves in Mindanao, at Del Carmen.^{[citation needed]} Long stretches of wetlands indicate a potential for commercial seaweed propagation. Siargao Island is greatly influenced by the winds and currents coming uninterrupted from the Pacific Ocean, intensified by the Mindanao current running westward through the Siargao Strait.

Offshore, a classic tropical island lies protected within its surrounding coral reef with dozens of coconut palms dressed in the center circle of the island. Off to the right, well within the massive coastal reef, lies a shining white sand bar, (Pansukian, or Naked island) some 200 meters long. The tide of Siargao is diurnal with tidal curves typically present, especially on the east coast of the island.