The Flat Hat Club is the popular name of a collegiate secret society and honor fraternity founded in 1750 at the College of William and Mary in Williamsburg, Virginia. The fraternity, formally named the "F.H.C. Society", was founded at the College on November 11, 1750. The society maintains relationships with societies at the University of St. Andrews and Amherst College.

The F.H.C. Society is the first recorded collegiate secret society in the United States of America. Early in the 20th century, the Education section of The New York Times profiled America's oldest university clubs and societies and included a letter (now in the archives held at Swem Library) which Thomas Jefferson wrote to Thomas McAuley, mentioning Jefferson's own membership of the F.H.C.