Polyommatus semiargus, the Mazarine blue, is a butterfly in the family Lycaenidae. The wingspan of the male and female are similar, at 32–38 mm. The Mazarine blue's population is distributed throughout continental Europe, even reaching into the Arctic Circle, Asia, the Middle East, and Morocco. There was a large native population in Britain in the early part of the 19th century, which disappeared before the 20th century, though single vagrants have been spotted, and some estimates of British resident extinction are as late as 1906. In 2009, UNESCO was researching a possible British reintroduction of the Mazarine blue to Britain.