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 in Crystal Lake was higher in 1990 than in 1981.