Icaricia lupini, the lupine blue, is a butterfly of the family Lycaenidae. It is found from south-western Canada, south through much of mountainous and intermountain western United States and high plains to northern Mexico. The wingspan is 22–29 mm. Adults are on wing from June to August in one generation in the Sierra Nevada of eastern California. Elsewhere, there are several generations from March to July. The larvae feed on Eriogonum umbellatum and Eriogonum fasciculatum. Adults feed on flower nectar. The hairs of the caterpillars can cause skin irritation (urticaria).