Willow Grove is a census-designated place (CDP) in Montgomery County, Pennsylvania. A community in Philadelphia's northern suburbs, the population was 15,726 at the 2010 census. It is located in Upper Dublin Township, Abington Township and Upper Moreland Township. Willow Grove was once known for Willow Grove Park, an amusement park that was open from 1896 to 1976, now the site of Willow Grove Park Mall. Willow Grove is considered an edge city of Philadelphia with large amounts of retail and office space.
Naval Air Station Joint Reserve Base Willow Grove was located northwest of the Willow Grove CDP in Horsham Township. NAS JRB Willow Grove transitioned into Horsham Air National Guard Station in September 2011.
Willow Grove is located at 40°08′46″N 75°07′00″W (40.146109, -75.116641).
According to the United States Census Bureau, the CDP has a total area of 3.6 square miles (9.3 km2), of which 0.28% is water. It has a hot-summer humid continental climate (Dfa) bordering upon a humid subtropical climate (Cfa) and its hardiness zone is 7a. Average monthly temperatures range from 31.8° F in January to 75.9° F in July. 
As of the 2010 census, the CDP was 81.4% White, 8.2% Black or African American, 0.2% Native American, 4.9% Asian, 1.1% were Some Other Race, and 2.3% were two or more races. 3.5% of the population were of Hispanic or Latino ancestry.
As of the census of 2000, there were 16,234 people, 6,389 households, and 4,255 families residing in the CDP. The population density was 4,485.7 people per square mile (1,731.5/km2).