Leo Stein (May 11, 1872 – July 29, 1947) was an American art collector and critic. He was born in Allegheny City (now in Pittsburgh), the older brother of Gertrude Stein. He became an influential promoter of 20th-century paintings.
Stein spent a number of years living in Paris with his sister. In 1914, the two separated due to Leo's resentment of Gertrude's infatuation with Alice B. Toklas, whom he described as "a kind of abnormal vampire."[1] Stein returned to America to work as a journalist but eventually settled near Florence, Italy, with his long-time love interest, Nina Auzias. They eventually married in 1921.[2]