A type of silver or gold coin widely used in Europe for many centuries. The first ducat was a silver coin issued around 1140 by King Roger II of Naples and Sicily (1105-1154) for his mainland duchy of Apulia, which he acquired in 1128. The coin bore the inscription SIT. T. XTE. D.Q. T.V. REG. ISTE. DUCAT., abbreviation for Sit tibi, Christe, datus, quem tu regis, iste Ducatus "May it be given to thee, Christ, this Duchy, which you rule".

In about 1280 Venice issued a gold coin called a ducat. One side featured Christ in glory, and the other the kneeling Doge receiving the gonfalon or sacred banner from the Venetian patron St Mark. It also bore the same Sit tibi inscription as the Apulian silver ducat. Under the name of ducat this pattern was widely imitated across Europe; though the Venetian coin itself later came to be known as the zecchino from the Palace of La Zecca where the Mint was located. The zecchino is better known in English under the French version of the name, sequin. It continued in use until the extinction of the Venetian Republic in 1797.

In the nineteenth century Britain started to follow the rest of Europe and convert to decimal currency. A florin of one tenth of a pound was issued in 1849, and though it never did entirely supersede the half crown (eighth of a pound), it continued in normal use until decimalisation, becoming the 10p coin in 1971. An alternative to dividing the pound into tenths and hundredths was to erect higher units of tens and hundreds of pence: this was proposed by the issue of a ducat of 100 pence in 1887, featuring an oak wreath. However this pattern coin never went into circulation.

Other countries issuing coins called ducats or patterned after the Venetian gold ducat included Austria (1612-1914), Russia, the Netherlands, and Sweden.

Chamberlain, 1960, The Teach Yourself Guide to Numismatics, English Universities Press
The 1911 Encyclopaedia