Mexicali Municipality is a municipality (Spanish: municipio) in the Mexican state of Baja California. Its municipal seat (Spanish: cabecera municipal) is located in the city of Mexicali. According to the 2010 census, it had a population of 936,826 inhabitants, and according to the 2000 census, it had 764,602 inhabitants, which means an increase of 22.5%. The municipality has an area of 13,700 km² (5,300 sq mi.) This includes many smaller outlying communities as well as the city of Mexicali. Also, the islands of Baja California located in the Gulf of California are part of the municipality, among them the mudflat islands at the mouth of the Colorado River (the largest one being Montague Island), Isla Ángel de la Guarda and the islands of the San Lorenzo Marine Archipelago National Park. Mexicali is the northernmost municipality of Latin America.
The city of Mexicali was founded in 1903, and its name is a portmanteau of Mexico and California, as is the name of Calexico, California across the border. This is an unusual pair of border cities in that Mexicali, on the Mexican side, is far larger than Calexico, on the U.S. side.