The White Lake fen is a small wetland on the shore of White Lake in Lanark County, Ontario in Canada. It has been designated both an Area of Natural and Scientific Interest and a Provincially Significant Wetland; it is also listed as a Special Place in Lanark County. Fens are a relatively rare wetland habitat in the region of Lanark County; they can occur on either marble or limestone bedrock. White lake has a granite dome along its north shore, while it spreads over marble bedrock to the south. A number of calcareous fens have developed along the south shore. The largest of these has developed in a long narrow arm of the lake, where it stretches for nearly two kilometers and covers 90 ha.