The pre-decimal threepence (3d), usually simply known as a threepence or threepenny bit, was a unit of currency equalling one eightieth of a pound sterling, or three pence sterling. It was used in the United Kingdom, and earlier in Great Britain and England.

Coins of the same size and virtually the same design (but with proof-like finish) have been issued regularly since 1817 and continue to be released every year as part of Maundy sets; these are listed separately under Maundy Threepence in the NCLT section; apart from the surface quality, they are indistinguishable.

Threepence coins issued in 1915 circulated for 56 years until "Decimal Day", 15 February 1971, and ceased to be legal tender after 31 August 1971. Unlike some of the larger denominations, they were not re-denominated to a decimal value when the decimal Pound Sterling was introduced.