Knightsen (formerly Knightsen Station) is a census-designated place (CDP) in Contra Costa County, California, in the United States. As of the 2010 census, the CDP population was 1,568, up from 861 reported in the 2000 census.
According to the United States Census Bureau, the CDP has a total area of 8.5 square miles (21.9 km²), 99% of it land.
The 2010 United States Census reported that Knightsen had a population of 1,568. The population density was 185.4 people per square mile (71.6/km²). The racial makeup of Knightsen was 1,268 (80.9%) White, 14 (0.9%) African American, 8 (0.5%) Native American, 28 (1.8%) Asian, 3 (0.2%) Pacific Islander, 162 (10.3%) from other races, and 85 (5.4%) from two or more races. Hispanic or Latino of any race were 454 persons (29.0%).