Mariposa County is a county located in the U.S. state of California. As of the 2020 U.S. Census, the population was 17,131. The county seat is Mariposa. It is located in the western foothills of the Sierra Nevada mountains, north of Fresno, east of Merced, and southeast of Stockton.

Mariposa is an unincorporated community and census-designated place (CDP) in and the county seat of Mariposa County, California, United States. The population was 1,526 at the 2020 census. The community is named after the flocks of monarch butterflies seen overwintering there by early explorers.