Oroville is a city in and the county seat of Butte County, California, United States. Its population was 15,506 at the 2010 census, up from 13,004 in the 2000 census. After the 2018 Camp Fire that destroyed much of the town of Paradise, Oroville's population increased as many people who lost their homes moved there. The 2020 census recorded Oroville's population as 20,042.