Challenger Deep is located near the U.S. territory of Guam. It lies in the western Pacific Ocean, at the southern end of the Mariana Trench, with Guam roughly 164 nautical miles to the northeast.
Although Guam is the nearest familiar U.S. territory, Challenger Deep is not inside Guam itself. The seabed feature is in the ocean territory of the Federated States of Micronesia, near the Mariana island chain. Its extreme depth is generally placed at roughly 10,900 to 11,000 metres below sea level, though modern surveys give slightly different measurements.
The feature was first identified during the 1872–1876 voyage of HMS Challenger, whose name it later received. The nearby-location wording can cause confusion: Wake Island and American Samoa are also Pacific U.S. territories, while Puerto Rico is in the Caribbean. None is as close to Challenger Deep as Guam.