The British sixpence piece, sometimes known as a tanner or sixpenny bit, was a denomination of sterling coinage worth 1⁄40 of one pound or half of one shilling. It was first minted in 1551, during the reign of Edward VI, and circulated until 1980. The coin was made from silver from its introduction in 1551 until 1947, and thereafter in cupronickel.

The first sixpences were minted in 1551, during the reign of Edward VI. They came about as a result of the debasement of silver coinage in the 1540s, in particular the silver testoon, which fell in value from 12d to 6d. The debased testoon was likely useful in everyday transactions, and it was decided that new coinage should be introduced with the express denomination of six pence. The testoon decreased in value because, unlike today, the value of coins was determined by the market value of the metal they contained, and during the reign of Henry VIII the purity of silver in coinage had fallen significantly.

Sixpences were minted during the reign of every British monarch after Edward VI, as well as during the Commonwealth, with a vast number of variations and alterations over the years. During the reign of George II a number of issues were designed by John Sigismund Tanner, who became Chief Engraver of the Royal Mint, and it has been suggested that this is the origin of the nickname "tanner", which was a popular name for the coin until decimalisation. An alternative explanation for the nickname is that it comes from the Angloromani word tawno meaning small thing.

The Royal Mint undertook a massive recoinage programme in 1816, with large quantities of gold and silver coin being minted. Previous issues of silver coinage had been irregular, and the previous issue, minted in 1787, had done little to alleviate the chronic shortage of silver coinage in general circulation. New silver coinage was to be of .925 (sterling) standard, with silver coins to be minted at 66 shillings to the pound weight. Hence, newly minted sixpences weighed 1⁄11 troy ounce, equivalent to 43.636 grains or 2.828 grams.