Peter Joseph Wagner (August 14, 1795 – September 13, 1884) was a U.S. Representative from New York.

Born at Wagners Hollow in the town of Palatine, New York, Wagner moved to Fort Plain, New York, with his parents in 1805. He completed preparatory studies. He attended Fairfield Academy in 1810 and 1811. He was graduated from Union College, Schenectady, New York, in 1816. He studied law. He was admitted to the bar in September 1819 and commenced practice at Fort Plain, New York. He also engaged in agricultural pursuits and banking. He was an unsuccessful candidate for election in 1834 to the Twenty-fourth Congress.

Wagner was elected as a Whig to the Twenty-sixth Congress (March 4, 1839 – March 3, 1841). He served as chairman of the Committee on Expenditures in the Department of War (Twenty-sixth Congress). He continued the practice of law at Fort Plain until May 1873, when he retired. He died at Fort Plain, New York, September 13, 1884. He was interred in Fort Plain Cemetery.