Countryside is a census-designated place in Loudoun County, Virginia, United States. The population as of the 2010 census was 10,072. It is located about 27 miles (43 km) northwest of Washington and is bounded by the Potomac River to the north, and by Route 7 (Leesburg Pike) to the south. Located in eastern Loudoun County, it is about 9 miles (14 km) north of Washington Dulles International Airport. It is bordered by the community of Cascades to the east and by Dulles Town Center to the south, across Route 7.

The Countryside subdivision was conceived in the middle 1970s when a tract of 1,000 acres (400 ha) of open farmland was subdivided in preparation for a planned housing development. Construction on homes began in 1981 and continued through 1991.

The Countryside CDP covers about 2.6 square miles (6.7 km) and homes in Countryside have a 20165 (Potomac Falls or Sterling) ZIP code.

The majority of the homes in Countryside were built by Pulte Homes and are of the colonial architectural style. Most of the single-family homes have two stories and a basement. CountrySide Proprietary is the community's homeowners association.

The community contains an extensive network of paved paths that wind through the wooded neighborhoods. It also contains three swimming pools. A network of smaller hiking trails branch off the main trail and are used for hiking, mountain biking, nature-watching and jogging. Some of the trails were developed by Eagle Scouts, others gradually by hikers; still others pre-date Countryside itself.

Horsepen Run drains the community, flowing north into the Potomac River. Countryside Lake is also accessible within the community for fishing and light water recreation at users' risk.

Several parks and recreational facilities are accessible to the northern border of the community, including Horsepen Run Countryside Nature Preserve, Algonkian Regional Park (which features Algonkian Golf Course), Potomac Lake Sportsplex, and Volcano Island Waterpark. The Algonkian Regional Park boat ramp provides access to the Potomac River for water sports. Several playgrounds are also accessible within the community.

Countryside students attend Countryside Elementary School, Algonkian Elementary School, Horizon Elementary School, River Bend Middle School, and Potomac Falls High School.

• Countryside Elementary School
• Algonkian Elementary School
• River Bend Middle School
• Potomac Falls High School
• CountrySide Proprietary website