Leon Frank Czolgosz ( CHOW-gawsh; May 5, 1873 – October 29, 1901) was an American steelworker and anarchist known for the assassination of President William McKinley, whom he shot on September 6, 1901, in Buffalo, New York. The president died on September 14 after his wound became infected. Caught in the act, Czolgosz was quickly tried, convicted, and executed seven weeks later on October 29, 1901.

While some American anarchists described his action as inevitable, motivated by what they saw as the country's brutal social conditions, others condemned Czolgosz for hindering the movement's goals by damaging its public perception.