International status and usage of the euro

The euro, which is the currency of the European Union member states in the eurozone, has been used internationally since its launch in 1999. On 1 January 2002, when the currency formally replaced 12 currencies of the original eurozone states, its usage was inherited in territories such as Montenegro which had used pre-euro currencies, while other minor currencies tied to pre-euro currencies were also replaced by the euro, such as in Monaco.

Source: Wikipedia — International status and usage of the euro (CC BY-SA 4.0)