Martin Alonzo Haynes (July 30, 1842 - November 28, 1919) was a U.S. Representative from New Hampshire.
Born in Springfield, New Hampshire, Haynes moved with his parents to Manchester in 1846. He attended the common schools and apprenticed to the printer's trade. At the outbreak of the Civil War, he enlisted in June 1861 in the Union Army as a private in the Second New Hampshire Regiment and served three years. He moved to Lakeport, New Hampshire, in 1868, where he established the Lake Village Times, which he conducted for twenty years.
Haynes served as member of the New Hampshire House of Representatives in 1872 and 1873. He served as clerk of the supreme court for Belknap County, 1876-1883. He served as president of the New Hampshire Veterans' Association in 1881 and 1882, and as department commander of the Grand Army of the Republic in 1881 and 1882.
Haynes was elected as a Republican to the Forty-eighth and Forty-ninth Congresses (March 4, 1883-March 3, 1887). He was an unsuccessful candidate for reelection in 1886 to the Fiftieth Congress. Subsequently, he was an internal-revenue agent of the Treasury, 1890–1893 and 1898-1912. He established the internal-revenue service in the Philippine Islands.
He died in Lakeport, New Hampshire, November 28, 1919, and was interred in Bayside Cemetery.