Guam National Wildlife Refuge, Wildlife refuge in Yigo, Guam.

Guam National Wildlife Refuge has three units: the Andersen Air Force Base Overlay Unit, the Navy Overlay Unit and the Ritidian Unit at Puntan Litekyan on Guam's northern tip. Ritidian covers about 1,217 acres, including 385 terrestrial acres and 832 submerged acres offshore, and is the only unit open to the public. Its shoreline lies below a former barrier reef now standing as a 500-foot limestone cliff.

The Navy operated a communications site here during the Cold War before donating approximately 1,200 acres to the Fish and Wildlife Service in 1993. This shift from military use to protected refuge status represented a major turning point for island conservation efforts.

The CHamoru name for the Ritidian Unit is Puntan Litekyan. The unit contains the archaeological site of a pre-Magellan CHamoru village, and its limestone cliff was once a barrier reef. The 1993 land transfer was opposed by Guam Delegate Robert A. Underwood, who argued it violated indigenous CHamoru land rights because the property was not returned to pre-military owners.

The Ritidian Unit offices and beaches close to the public at 4 PM every day. They also shut whenever Guam Homeland Security's Office of Civil Defense issues tropical cyclone condition of readiness 3, 2 or 1, and the beaches close during National Weather Service tropical storm warnings. Check conditions before setting out.

The single mature Serianthes nelsonii tree known on Guam stands in the military overlay units, where the University of Guam coordinates planting of new seedlings. The Ritidian Unit holds the island's only designated critical habitat, declared in 2004 for the Mariana fruit bat, Guam Micronesian Kingfisher and Mariana crow.