Leon Rosen (March 1869, Warsaw – 16 August 1942, New York City) was an American chess master.
Born in Warsaw, Poland (then Russian Empire), he left for Paris, France, and next emigrated to the United States.
He took 4th at Paris 1896 (Dawid Janowski won), and took 14th in the Paris 1900 chess tournament (Emanuel Lasker won).
In that time, he appeared on the New York 1900 Census.
He took 18th at Excelsior 1905 (U.S.
Open Chess Championship, Edward F.
Schrader won), took 2nd, after Julius Finn, in the 1907 New York State championship, took 2nd, behind Clarence S.
Howell, at Trenton Falls 1908 (Quadrangular).
In 1909, he shared 1st with Manuel Ayala and Otto Roething in the Manhattan CC championship.