The Marianas Trench Marine National Monument is a United States National Monument created by President George W. Bush by the presidential proclamation no. 8335 on January 6, 2009. The monument includes no dry land area, but protects 95,216 square miles (246,610 km2) of submerged lands and waters in various places in the Mariana Archipelago. The United States could create this monument under international law because the maritime exclusive economic zones of the adjacent Northern Mariana Islands and Guam fall within its jurisdiction.

In the United States, a national monument is a protected area that can be created from any land owned or controlled by the federal government by proclamation of the president of the United States or an act of Congress. National monuments protect a wide variety of natural and historic resources, including sites of geologic, marine, archaeological, and cultural importance. In contrast, national parks in the U.S. must be created by Congressional legislation. Some national monuments were first created by presidential action and later designated as national parks by congressional approval.