Tiffin is a city in Johnson County, Iowa, United States. It is part of the Iowa City, Iowa Metropolitan Statistical Area. The population was 4,512 at the time of the 2020 census. F. W. Kent County Park is located just to the west of Tiffin, and is a popular site for outdoor recreation in Johnson County, being noted for its lake, camping facilities, resident whitetail deer herd and wild turkeys, and its cross-country ski trails through rolling acres of oak and hickory forest.