Cornelius is a city in Washington County, Oregon, United States. The population was 9,652 at the 2000 census. The 2007 estimate is 10,895 residents.
According to the United States Census Bureau, the city has a total area of 1.9 square miles (4.9 km²), all of it land.
As of the census of 2000, there were 9,652 people, 2,880 households, and 2,246 families residing in the city. The population density was 5,095.9 people per square mile (1,971.8/km²). There were 3,003 housing units at an average density of 1,585.5 per square mile (613.5/km²). The racial makeup of the city was 37.39% White, 0.76% African American, 1.24% Native American, 1.04% Asian, 0.28% Pacific Islander, 24.32% from other races, and 3.76% from two or more races. Hispanic or Latino of any race were 68.61% of the population.