Isaac Leffler (November 7, 1788 – March 8, 1866), sometimes spelled Lefler or Loeffler, was an American lawyer who represented Virginia's 18th congressional district in the United States House of Representatives for one term in the 1820s; and served in the legislatures of the Commonwealth of Virginia and of the Wisconsin and Iowa Territories.
He was the older brother of Iowa U.S.
Representative Shepherd Leffler, who served in Congress twenty years later.