Hydrelia flammeolaria, the small yellow wave, is a moth of the family Geometridae. The species was first described by Johann Siegfried Hufnagel in 1767 It is found in most of the Palearctic realm, from western Europe to Japan. There is one generation per year, with adults on wing from mid-May to August. The larvae feed on various deciduous trees, including Alnus (including Alnus glutinosa and Alnus incana) and Acer (including Acer campestris) species. Larvae can be found from July to September. It overwinters as a pupa.