Mono County is a county located in the east central portion of the U.S. state of California. As of the 2020 census, the population was 13,195, making it the fourth-least populous county in California. The county seat is Bridgeport. The county is located east of the Sierra Nevada between Yosemite National Park and Nevada. The only incorporated town in the county is Mammoth Lakes, which is located at the foot of Mammoth Mountain.