Fissidens fontanus, commonly known as limp pocket moss or phoenix moss, is a species of aquatic moss belonging to the family Fissidentaceae.
Fissidens fontanus is a pleurocarpic moss that has lance-like leaves with a conspicuous midrib that are around 2-7mm in length. At the base of each leaf, a small folded over lobe is formed resembling a pocket. Leaves have an alternating orientation on the stem, ending in a small tuft of gathered leaves.
Sporophytes are located on the stem of F. fontanus, often located in the leaf base. The capsules are short, under around 1mm, and erectly point away from the stem.
Fissidens fontanus has a wide distribution, and has been found across Europe, the Mediterranean, North America, Mexico, Chile, Australia, Zambia, and the Arabian Peninsula. F. fontanus can be found in both natural and man-made aquatic environments, and seems to be somewhat tolerant of pollutants. F. fontanus is typically found in slow-moving or still water. While this moss is considered to be an aquatic species, it can be found growing emerged in areas where the water levels vary seasonally.