Massachusetts House of Representatives' 4th Hampden district in the United States is one of 160 legislative districts included in the lower house of the Massachusetts General Court. It covers the city of Westfield in Hampden County. Democrat John Velis of Westfield represented the district from 2014 to 2020. Candidates for this district seat in the 2020 Massachusetts general election include Independent Conservative Dan Allie, Democrat Matt Garlo, and Republican Kelly Pease.

Westfield is a city in Hampden County, in the Pioneer Valley of western Massachusetts, United States. Westfield was first settled by Europeans in 1660. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. The population was 40,834 at the 2020 census.