Lower California (Spanish: Baja California, bä'hä), a peninsula of Mexico lying between the Pacific Ocean and the Gulf of California. It is about 780 miles (1,255 km) long and from 30 to 140 miles (48 to 225 km) wide, with an area of 55,518 square miles (143,791 km2). The northern part forms the Mexican state of Baja California (capital: Mexicali); the southern part, the state of Baja California Sur (capital: La Paz).

Except for a few coastal plains, the peninsula consists largely of rough plateaus and mountains. A few peaks reach elevations of 6,000 feet (1,830 m); one reaches 10,065 feet (3,068 m). Nearly everywhere the land is desolate and extremely hot and dry. Until the opening of a 1,000-mile (1,600-km) transpeninsular highway in 1973, most of it was virtually inaccessible.

Economic activities other than subsistence farming and coastal fishing are limited largely to the extreme north. Commercial agriculture is important along the Colorado River, where irrigation water is available and cotton is the chief crop. Most of the manufacturing is at Mexicali and Tijuana, both on the California border. Also significant are commercial fishing, at Ensenada, and tourism, chiefly in Tijuana and the southern tip of the peninsula. The vast majority of Lower California's population of 2,911,216 is concentrated in and around Tijuana, Mexicali, and Ensenada. Elsewhere, scattered small villages prevail.

The first Europeans to discover and explore the peninsula were Spaniards, in the 1530's. Colonization began in 1697, when Loreto, the first of a series of Jesuit missions, was founded. Lower California was detached from Spanish Upper (Alta) California in 1772. It became a territory in 1829. In 1887 it was divided into separate northern and southern territories. The northern part was made a state in 1951, the southern part in 1974.