John Ganson (January 1, 1818 – September 28, 1874) was an American lawyer and politician who served one term as a U.S. Representative from New York from 1863 to 1865.

Born in Le Roy, New York, Ganson attended the public schools and Le Roy Academy.

He graduated from Harvard University in 1839 and subsequently studied law.

He served as delegate to the 1864 Democratic National Convention.

He died in Buffalo on September 28, 1874, and was buried at the Forest Lawn Cemetery.