James Sidney Mercer (August 4, 1880 – June 19, 1945) was an American sports writer who covered mostly boxing and baseball in St. Louis and in New York City.

Mercer was born to James H. and Laura Ann Search Mercer on August 4, 1880, in Kerr Township, Champaign County, Illinois, where his father farmed and attended school in nearby Paxton, Illinois.

[1] Mercer began his career as a printer's apprentice with the St. Louis Republic.

The following year, Mercer was hired at the New York Evening Globe.

He was a charter member of the Baseball Writers' Association of America (BBWAA).