David Henry Mercer (Born 1857- d. 1919) was a Nebraska Republican politician. Born in Benton County, Iowa on July 9, 1857, he moved with his parents to Adams County, Illinois in 1858. After the American Civil War he moved again to Brownville, Nebraska. He graduated from the University of Nebraska-Lincoln in 1880 and the law department of Michigan University in Ann Arbor, Michigan in 1882. He was admitted to the bar and set up practice back in Brownville serving one term as city clerk and police judge.
He moved to Omaha, Nebraska in 1885 and was for several years was chairman of the Republican city and county committees. He was the secretary of the Republican State central committee in 1896, and elected secretary of the Republican National Congressional Committee in the same year. In 1897 he was chairman of the Republican State Central committee of Nebraska in 1897 and 1898.
He was elected as a Republican to the Fifty-third United States Congress and to the four succeeding Congresses serving from March 4, 1893 to March 3, 1903. During his time as representatives he was chairman of the U.S. House Committee on Public Buildings and Grounds during the Fifty-fifth, Fifty-sixth, and Fifty-seventh Congresses. He unsuccessfully ran for reelection in 1902. Afterwards he settled in Washington, D.C. resuming his practice of law. He died in Omaha on January 10, 1919 and is buried in Forest Lawn Cemetery, in Omaha..
Preceded by: William A. McKeighan (P) Member of the U.S. House of Representatives from Nebraska's 2nd congressional district March 4, 1893 - March 3, 1903 Succeeded by: Gilbert M. Hitchcock (D)