Willoughby Hills is a city in Lake County, Ohio, United States. The population was 9,485 at the 2010 census.
Willoughby Hills is located at 41°35′17″N 81°26′33″W (41.588151, -81.442475).
According to the United States Census Bureau, the city has a total area of 10.82 square miles (28.02 km2), of which 10.73 square miles (27.79 km2) is land and 0.09 square miles (0.23 km2) is water. Willoughby Hills borders Euclid and Richmond Heights on the west, Gates Mills, Highland Heights, and Mayfield Village on the south, Kirtland and Waite Hill on the east, and Wickliffe and Willoughby to the north.
88.3% spoke English, 3.7% Slovene, 3.1% Croatian, 1.1% Spanish, 1.1% Italian, and 1.1% Russian.
Of the city's population over the age of 25, 35.5% held a bachelor's degree or higher.
As of the census of 2010, there were 9,485 people, 4,398 households, and 2,602 families living in the city. The population density was 884.0 inhabitants per square mile (341.3/km2). There were 4,929 housing units at an average density of 459.4 per square mile (177.4/km2). The racial makeup of the city was 77.6% White, 16.1% African American, 4.3% Asian, 0.3% from other races, and 1.6% from two or more races. Hispanic or Latino of any race were 1.3% of the population.
There were 4,398 households, of which 23.0% had children under the age of 18 living with them, 44.6% were married couples living together, 10.4% had a female householder with no husband present, 4.1% had a male householder with no wife present, and 40.8% were non-families.