Williamsfield is a village in Knox County, Illinois, United States. The population was 620 at the 2000 census. It is part of the Galesburg Micropolitan Statistical Area.
Williamsfield is located at 40°55′26″N 90°1′3″W / 40.92389°N 90.0175°W / 40.92389; -90.0175 (40.923962, -90.017626).
According to the United States Census Bureau, the village has a total area of 1.3 square miles (3.3 km²), all of it land.