薄网藓（学名：Leptodictyum riparium）为青藓科薄网藓属下的一个种。

Leptodictyum riparium, commonly known as Kneiff's feathermoss, streamside leptodictyum moss, or knapwort, is a species of moss commonly found growing in the lakes and rivers of Minnesota and also Mexico, Guatemala, the Bahamas archipelago, Cuba, Jamaica, Haiti, Dominican Republic, Venezuela, Peru and Brazil. However, the only places it is not found are the Pacific Islands and Australia. This moss has several different forms and can grow up to 30 cm and its ovate leaves which are in two rows are often pointed at their apex. Leptodictyum riparium was also once found in an acidic neutral mining lake and can live at a pH down to 1.6 in volcanic craters and also once found with Eleocharis acicularis at a Canadian mining lake. It is known to contain high levels of phosphate and is an easy to grow moss that is also used in aquariums. It has also been reported that leptodictyum riparium has a large range of nutrient conditions and its population increases as ammonia increases.