Los Angeles often referred to by its initials L.A., is the largest city in California. With a 2020 population of 3,898,747,it is the second-largest city in the United States, following New York City. Los Angeles is known for its Mediterranean climate, ethnic and cultural diversity, Hollywood film industry and sprawling metropolitan area.

The City of Los Angeles lies in a basin in Southern California, adjacent to the Pacific Ocean, and extends through the Santa Monica Mountains and into the San Fernando Valley, covering a total of about 469 square miles (1,210 km2). It is the seat of Los Angeles County, which is the most populous county in the United States.

Home to the Chumash and Tongva indigenous peoples, the area that became Los Angeles was claimed by Juan Rodríguez Cabrillo for Spain in 1542. The city was founded on September 4, 1781, under Spanish governor Felipe de Neve, on the village of Yaanga. It became a part of Mexico in 1821 following the Mexican War of Independence. In 1848, at the end of the Mexican–American War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, and thus became part of the United States. Los Angeles was incorporated as a municipality on April 4, 1850, five months before California achieved statehood. The discovery of oil in the 1890s brought rapid growth to the city. The city was further expanded with the completion of the Los Angeles Aqueduct in 1913, which delivers water from Eastern California.

Los Angeles has a diverse and robust economy, and hosts businesses in a broad range of professional and cultural fields. It also has the busiest container port in the Americas. In 2018, the Los Angeles metropolitan area had a gross metropolitan product of over $1.0 trillion, making it the city with the third-largest GDP in the world, after Tokyo and New York City. Los Angeles hosted the 1932 and 1984 Summer Olympics and will host the 2028 Summer Olympics.