A thaler (; also taler, from German: Taler) is one of the large silver coins minted in the states and territories of the Holy Roman Empire and the Habsburg monarchy during the Early Modern period. A thaler size silver coin has a diameter of about 40 mm (1+1⁄2 in) and a weight of about 25 to 30 grams (roughly 1 ounce). The word is shortened from Joachimsthaler, the original thaler coin minted in Joachimstal, Bohemia, from 1520.

While the first standard coin of the Holy Roman Empire was the Guldengroschen of 1524, its longest-lived coin was the Reichsthaler (Reichstaler), which contained 1⁄9 Cologne Mark of fine silver (or 25.984 g), and which was issued in various versions from 1566 to 1875. From the 17th century a lesser-valued North German thaler currency unit emerged, which by the 19th century became par with the Vereinsthaler.

The thaler silver coin type continued to be minted until the 20th century in the form of the Mexican peso until 1914, the five Swiss franc coin until 1928, the US silver dollar until 1935, and the Austrian Maria Theresa thaler. These days thaler-sized silver coins are not in active circulation anymore, but are minted by various government mints as bullion or numismatic items for collectors. The English derivative of the name, dollar, also survives as the name of several modern currencies.