Catherine Mitchell Gregg (August 15, 1917 – August 1, 2014) was an American philanthropist, environmentalist and historic preservationist. Gregg served as the First Lady of New Hampshire from 1953 until 1955 during the administration of her husband, former Governor Hugh Gregg. She was also the mother of another former Governor of New Hampshire, U.S. Representative, and U.S. Senator, Judd Gregg. An active philanthropist, Catherine Gregg led efforts to preserve and restore the Wentworth-Coolidge Mansion in Portsmouth, the last surviving, original colonial era Royal Governor's residence in the United States.