John Robert Marks III (born July 25, 1947) is an American lawyer, politician, and former Mayor of Tallahassee, Florida from February 2003 until November 2014.

Marks served eight years on the Florida Public Service Commission[3] (FPSC) and spent the last two as its chairman, after being appointed in 1979 by Governor Bob Graham.

He served on the FPSC during the divestiture of AT&T and was instrumental in the implementation of the Federal Public Utility Regulatory Policies Act (PURPA).

On January 4, 2003, Marks' predecessor, then-Tallahassee Mayor Scott Maddox, was elected Chairman of the Florida Democratic Party.

[6] His closest opponent, John Paul Bailey, a Republican Tallahassee City Commissioner and former police officer, placed second with 27% of the vote.