Ridgefield is an unincorporated community and census-designated place in McHenry County, Illinois, United States. Ridgefield is northwest of Crystal Lake. It was named a CDP before the 2020 census, at which time it had a population of 210.
A post office called Ridgefield was first established in 1858. The community was named from the ridges near the town site.
Ridgefield first appeared as a census designated place in the 2020 U.S. census.