Joseph Wayne Mercer (February 25, 1845 – March 13, 1906) was an American politician from Missouri.

He attended Chapel Hill College in Lafayette County, Missouri.

During the American Civil War, he served in Confederate Army, and was wounded at the battles of Lexington, Pea Ridge, and Pine Bluff, losing his right arm in the latter.

[2] Entering politics, he was elected to the Independence City Council, and later served as Treasurer of Jackson County, Missouri.

Following his term as state treasurer, he returned to Independence, where he worked in the banking and grocery industries.