The Flat Hat Club is a collegiate secret society and honor society at the College of William & Mary in Williamsburg, Virginia. Originally called the F.H.C. Society, it was founded in 1750.
Early in the 21st century, the education section of The New York Times profiled America's oldest university clubs and societies and included a letter, now housed in the archives at Swem Library, which Thomas Jefferson wrote to Thomas McAuley, mentioning Jefferson's membership in the F.H.C.