West Springfield is a city in Hampden County, Massachusetts, United States. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. The population was 28,835 at the 2020 United States Census. The city is also known as "West Side", in reference to the fact that it is on the western side of the Connecticut River from Springfield, a fact which played a major part in the town's early history.

Hampden County is a non-governmental county located in the Pioneer Valley of the U.S. state of Massachusetts, in the United States. As of the 2020 census, Hampden County's population was 465,825. Its traditional county seat is Springfield, the Connecticut River Valley's largest city, and economic and cultural capital; with an estimated population of 154,758, approximately one-third of Hampden County residents live in Springfield.