David Fulton "Dave" Karsner (1889–1941) was an American journalist, writer, and socialist political activist. Karsner is best remembered as a key member of the editorial staff of the New York Call and as an early biographer of Socialist Party of America leader Eugene V. Debs.
David Karsner was born March 13, 1889 at Baltimore, Maryland, the son of Cecil J. and Anita Karsner. The elder Karsner worked as an official at the Port of Baltimore.
Both of Karsner's parents died when David was still young and he wound up in a Baltimore orphanage and school for underprivileged boys.
Karsner's journalistic career began about 1907 when he went to work for a newspaper in the city of Chicago. While in Chicago Karsner made the acquaintance of a number of socialist intellectuals, including Upton Sinclair, Jack London, and Carl Sandburg. His discussions with these led Karsner himself to become an advocate of socialism and to join the Socialist Party of America.
Karsner's journalistic career took him to Philadelphia, where he joined the staff of the Philadelphia Ledger, and to New York City, where he worked for the New York Tribune and the New York Post.
In 1911 Karsner married the Romanian-born socialist Rose Greenberg (1889–1968). The pair had a daughter, Walta Karsner, named after radical poet Walt Whitman. Following the dissolution of their marriage, Rose Karsner married James P. Cannon, regarded as the founder of American Trotskyism, while David Karsner remarried to Esther Eberson.