The National Museum of Natural History (NMNH) is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. With 4.4 million visitors in 2023, it was the second most-visited museum in the United States.

The Smithsonian Institution, or simply the Smithsonian, is a group of museums, education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge." Founded on August 10, 1846, it operates as a trust instrumentality and is not formally a part of any of the three branches of the federal government. The institution is named after its founding donor, British scientist James Smithson. It was originally organized as the United States National Museum, but that name ceased to exist administratively in 1967.