El Camino Real (Spanish; literally The Royal Road, sometimes translated as The King's Highway) is a 600-mile (965-kilometer) commemorative route connecting the 21 Spanish missions in California (formerly the region Alta California in the Spanish Empire) from Mission San Diego de Alcalá in San Diego to Mission San Francisco Solano in Sonoma, along with a number of sub-missions, four presidios, and three pueblos. The route is historically associated with a network of royal roads (caminos reales) used by inhabitants of New Spain. The modern commemorative route in the U.S. state of California is named after these roads, and is officially defined in the California Streets and Highways Code to run along various roads from Interstate 5 at the Mexican border to State Route 12 in Sonoma.

During the period of Spanish rule, there was no single road constructed by the Spanish to connect the missions, with most of the network of royal roads following historic Native American trading routes. These various caminos reales covered much of what is today California, but with no single special route designated to link the missions. The name was revived in the American era in connection with the boosterism associated with the Mission Revival movement of the early 20th century. Streets throughout California bear the "El Camino Real" name. The route has been continually upgraded and is decorated with commemorative bell markers.

In earlier Spanish colonial times, any road under the direct jurisdiction of the Spanish crown and its viceroys was considered to be a camino real. Examples of such roads ran between principal settlements throughout Spain and its colonies such as New Spain. Most caminos reales had names apart from the appended camino real. Missions were present in Las Californias for decades before the establishment of any missions in what is today the U.S. state of California, with various Spanish missions established in present-day Baja California, Mexico, starting in 1697 with the Misión de Nuestra Señora de Loreto Conchó in present-day Loreto.

The Portolá expedition of 1769 included Franciscan missionaries, led by Junípero Serra. Starting from Loreto, Serra established the first of the 21 missions at San Diego. Serra stayed at San Diego and Juan Crespí continued the rest of the way with Gaspar de Portolá. Proceeding north, Portolá followed the coastline (today's California State Route 1), except where forced inland by coastal cliffs.

Eventually, the expedition was prevented from going farther north by the entrance to San Francisco Bay, the Golden Gate. Crespí identified several future mission sites which were not developed until later. On the return trip to San Diego, Gaspar de Portolá found a shorter detour around one stretch of coastal cliffs via Conejo Valley.^{[citation needed]}

Portolá journeyed again from San Diego to Monterey in 1770, where Junipero Serra (who traveled by ship) founded the second mission (later moved a short distance south to Carmel). Carmel became Serra's Alta California mission headquarters.

The Juan Bautista de Anza expedition of (1775–76) entered Alta California from the southeast (crossing the Colorado River near today's Yuma, Arizona), and picked up Portolá's trail at Mission San Gabriel. De Anza's scouts found easier traveling in several inland valleys, rather than staying on the rugged coast. On his journey north, de Anza traveled the San Fernando Valley and Salinas Valley. After detouring to the coast to visit the Presidio of Monterey, de Anza went inland again, following the Santa Clara Valley to the southern end of San Francisco Bay and on up the east side of the San Francisco Peninsula.

Between 1683 and 1835, Jesuit and Franciscan missionaries established a series of religious outposts from today's Baja California and Baja California Sur into present-day California. Heavy freight and long-distance passenger movement was practical only via ships by a coastal water route.