David Henry Mercer (July 9, 1857 – January 10, 1919) was an American Republican Party politician.

After the American Civil War he moved again to Brownville, Nebraska.

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.

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.