Clitocybe rivulosa, commonly known as the false champignon or fool's funnel, is a poisonous basidiomycete fungus of the large genus Clitocybe. One of several species similar in appearance, it is a small white funnel-shaped toadstool widely found in lawns, meadows and other grassy areas in Europe and North America. Also known as the sweating mushroom, it derives this name from the symptoms of poisoning. It contains potentially deadly levels of muscarine.