Brookside is a census-designated place (CDP) in New Castle County, Delaware, United States. The population was 14,353 at the 2010 census.

Brookside is located at 39°40′9″N 75°43′5″W / 39.66917°N 75.71806°W / 39.66917; -75.71806 (39.669211, -75.717961).

According to the United States Census Bureau, the CDP has a total area of 3.9 square miles (10 km²), all of it land.

At the 2000 census, there were 14,806 people, 5,465 households and 3,858 families residing in the CDP. The population density was 3,787.7 per square mile (1,462.1/km²). There were 5,645 housing units at an average density of 1,444.1 per square mile (557.4/km²). The racial makeup of the CDP was 77.35% White, 15.03% African American, 0.32% Native American, 2.61% Asian, 0.07% Pacific Islander, 2.22% from other races, and 2.40% from two or more races. Hispanic or Latino of any race were 5.59% of the population.

There were 5,465 households of which 35.9% had children under the age of 18 living with them, 49.9% were married couples living together, 15.4% had a female householder with no husband present, and 29.4% were non-families. 22.1% of all households were made up of individuals and 6.8% had someone living alone who was 65 years of age or older. The average household size was 2.68 and the average family size was 3.15.

Delaware (ⁱ/ˈdɛləwɛər/ DEL-ə-wair) is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, to the northeast by New Jersey, and to the north by Pennsylvania. The state takes its name from Thomas West, 3rd Baron De La Warr, an English nobleman and Virginia's first colonial governor, after whom what is now called Cape Henlopen was originally named.

Delaware is located in the northeastern portion of the Delmarva Peninsula and is the second least extensive, the sixth least populous, but the sixth most densely populated of the 50 United States. Delaware is divided into three counties. From north to south, these three counties are New Castle, Kent, and Sussex. While the southern two counties have historically been predominantly agricultural, New Castle County has been more industrialized.

The history of the state's economic and industrial development is closely tied to the impact of the Du Pont family, founders and scions of E. I. du Pont de Nemours and Company, one of the world’s largest chemical companies.