Johnstonville is a small unincorporated community in Lassen County, California. It is situated in the northeastern part of the state, near the city of Susanville. The area around Johnstonville provides numerous outdoor activities. It at an elevation of 4131 feet (1259 m). Its population is 973 as of the 2020 census, down from 1,024 from the 2010 census.