Shasta County, officially the County of Shasta, is a county located in the northern portion of the U.S. state of California. Its population is 182,155 as of the 2020 census, up from 177,223 from the 2010 census. The county seat is Redding. The County borders Modoc County, Lassen County, Siskiyou County, Plumas County, Tehama County and Trinity County.