Bisporella citrina, commonly known as yellow fairy cups or lemon discos, is a species of fungus in the family Helotiaceae. The fungus produces tiny yellow cups up to 3 mm (0.12 in) in diameter, often without stalks, that fruit in groups or dense clusters on decaying deciduous wood that has lost its bark. The widely distributed species is found in North Africa, Asia, Europe, North America, and Central and South America.