Leo Stein, born Leo Rosenstein was a playwright and librettist of operettas in the latter part of the 19th and early 20th centuries, including works adapted for a number of Broadway productions.

Stein wrote libretti for Johann Strauss Jr, Franz Lehár, Emmerich Kálmán, and Oskar Nedbal. His collaboration with Viktor Léon contributed much to Lehár's success.

A selection of his works includes Wiener Blut (1899), Die lustige Witwe (1905), Der Graf von Luxemburg (1909) and Die Csárdásfürstin (1915).[1]

Stein is buried at the Vienna Zentralfriedhof.