The Carrizo Plain is a large enclosed grassland plain, approximately 50 miles (80 km) long and up to 15 miles (24 km) across, in southeastern San Luis Obispo County, California, United States, about 100 miles (160 km) northwest of Los Angeles. The southern portion of the Carrizo Plain is within the 246,812-acre (99,881 ha) Carrizo Plain National Monument, which also includes most of the Caliente Range. The Carrizo Plain is the largest single native grassland remaining in California. It includes Painted Rock in the Carrizo Plain Rock Art Discontiguous District, which is listed on the National Register of Historic Places. In 2012 it was further designated a National Historic Landmark due to its archeological value. The San Andreas Fault occurs along the eastern edge of the Carrizo Plain at the western base of the Temblor Range.

San Luis Obispo County, officially the County of San Luis Obispo, is a county on the Central Coast of California. As of the 2020 census, the population was 282,424. The county seat is San Luis Obispo.