Mill Creek is a village in Union County, Illinois, United States.

The community is located on the west side of the Mill Creek floodplain just north of the Union-Alexander county line.

There were 31 housing units at an average density of 84.7 per square mile (32.7/km2).

27.6% of all households were made up of individuals, and 10.3% had someone living alone who was 65 years of age or older.

There were 36.8% of families and 36.9% of the population living below the poverty line, including 33.3% of under eighteens and 50.0% of those over 64.