The Territory of New Mexico was an organized incorporated territory of the United States from September 9, 1850, until January 6, 1912. It was created from the U.S. provisional government of New Mexico, as a result of Nuevo México becoming part of the American frontier after the Treaty of Guadalupe Hidalgo. It existed with varying boundaries until the territory was admitted to the Union as the U.S. state of New Mexico. This jurisdiction was an organized, incorporated territory of the US for nearly 62 years, the longest period of any territory in the contiguous United States.

Santa Fe de Nuevo México was a province of the Spanish Empire and New Spain, and later a territory of independent Mexico. The first capital was San Juan de los Caballeros from 1598 until 1610, and from 1610 onward the capital was La Villa Real de la Santa Fe de San Francisco de Asís.