The Adonis blue (Lysandra bellargus, also known as Polyommatus bellargus) is a butterfly in the family Lycaenidae. It inhabits the Palearctic realm (Western Europe, Central Europe, Southern Europe, Southern Russia, Iraq, Iran, Caucasus, Transcaucasus, and Turkey).
It is found in chalk downland, in warm, sheltered spots, flying low over vegetation, seeking females that are rich chocolate brown in color. The male has brilliantly colored blue wings that give it its name.