By Russell Berman and Josh Lederman - 11/28/11 08:58 PM EST
Frank, 71, is the top Democrat on the Financial Services Committee and the architect, with former Sen. Chris Dodd (D-Conn.), of the sweeping Wall Street regulatory reform law enacted in 2010.
He announced his decision at an afternoon press conference in his hometown of Newton, Mass., where he said redistricting played a major role in his retirement.
Frank said his decision was "precipitated by congressional redistricting, not entirely caused by it."
"There are other things I'd like to do in my life before my career is over," he said, referencing an uncompleted doctoral dissertation at Harvard University.