The Californias, occasionally known as The Three Californias or Two Californias, are a region of North America spanning the United States and Mexico, consisting of the U.S. state of California and the Mexican states of Baja California and Baja California Sur. Historically, the term Californias was used to define the vast northwestern region of Spanish America, as the Province of the Californias, and later as a collective term for Alta California and the Baja California Peninsula.

Baja California, officially Estado Libre y Soberano de Baja California, is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of Baja California. It has an area of 70,113 km2 (27,071 sq mi) and comprises the northern half of the Baja California Peninsula, north of the 28th parallel, plus oceanic Guadalupe Island. The mainland portion of the state is bordered on the west by the Pacific Ocean; on the east by Sonora, the U.S. state of Arizona, and the Gulf of California; on the north by the U.S. state of California; and on the south by Baja California Sur.