The freshwater red algae are a threatened algal group in many European countries. It is often overlooked by ecologists and taxonomists due to rarity and also to taxonomic difficulties and lack of suitable identification keys. Besides a glossary and a short introduction to the ecology of freshwater red algae this guide contains list of taxa found in Finland, and also lists of taxa recorded in Sweden, Poland and Austria are given. Two keys are provided, one including all freshwater red algal genera, and the other containing all filamentous, pseudoparenchymatic and parenchymatic taxa found in Finland. Altogether 27 species are so far recorded from Finland, and they belong to the genera Bangia, Audouinella, Batrachospermum, Sirodotia, Tuomeya, Lemanea, and Hildenbrandia. All species found in Finland are described in detail with drawings, colour photographs and distribution maps. In addition to them some other genera (Thorea and Paralemanea) occurring in Europe are described in detail.