In economics, bimetallism is a monetary standard where the value of the monetary unit can be expressed either with a certain amount of gold or with a certain amount of silver: the ratio between the two metals is fixed by law.

This monetary system is very unstable: due to the fluctuation of the commercial value of the metals, the metal with a commercial value higher than the currency value tends to be used as metal and is withdrawn from circulation as money (Gresham's Law).

Due to this instability, all the countries that used a bimetallic standard switched to the gold standard at the end of the 19th century.