Crystal Lake is a census-designated place (CDP) in Polk County, Florida, United States. The population was 5,341 at the 2000 census, an increase from 5,300 in 1990. The 2010 Census reported a population of 5,514. It is part of the Lakeland–Winter Haven Metropolitan Statistical Area.
The population of Crystal Lake grew by more than 200 from 2000 to 2010.