Leominster is a city in Worcester County, Massachusetts, United States. It is the second-largest city in Worcester County, with a population of 43,222 at the 2023 census. Leominster is located north of Worcester and northwest of Boston. Both Route 2 and Route 12 pass through Leominster. Interstate 190, Route 13, and Route 117 all have starting/ending points in Leominster. Leominster is bounded by Fitchburg and Lunenburg to the north, Lancaster to the east, Sterling and Princeton to the south, and Westminster to the west.

Worcester County is a county in the U.S. state of Massachusetts. At the 2020 census, the population was 862,111, making it the second-most populous county in Massachusetts. It is also the largest county in Massachusetts by geographic area. The largest city and traditional shire town is Worcester. Worcester County is part of the Worcester, MA–CT metropolitan statistical area and the Boston-Worcester-Providence combined statistical area.