Fillmore County is a county in the U.S. state of Minnesota. As of the 2020 census, the population was 21,228. Its county seat is Preston. Fillmore County is included in the Rochester metropolitan area.

Preston is a city and the county seat of Fillmore County, Minnesota, United States. The population was 1,325 at the 2010 census. The Root River runs through it, and Mystery Cave State Park is nearby. It bills itself as "America's Trout Capital," with a 20-foot trout placed along Minnesota State Highway 16.