Triangle is a census-designated place (CDP) in Prince William County, Virginia, United States.

According to the U.S. Census Bureau, Triangle has a total area of 2.6 square miles (6.8 km2), all of which is land.

29.7% of all households were made up of individuals, and 3.6% had someone living alone who was 65 years of age or older.

In the 1950 United States census, Triangle was combined with Dumfries, Virginia to form Dumfries-Triangle.

Triangle is part of Virginia's 31st House of Delegates district; as of 10 January 2018[[[Virginia House of Delegates election, 2017]] [ref]], residents are represented by Elizabeth Guzmán.