John A. McMahon (February 19, 1833 – March 8, 1923) was a three-term United States Representative from Ohio from 1875 to 1881.

McMahon was born in Frederick County, Maryland, and graduated from St. Xavier College in 1849.

[2] He was elected to the Forty-fourth, Forty-fifth, and Forty-sixth United States Congresses, from 1875 until 1881.

McMahon was appointed by the House of Representatives as a manager to conduct impeachment proceedings against Secretary of War William W. Belknap.

He served as the president of the Ohio State Bar Association in 1886,[3] and was a losing candidate for the Senate in 1889.