EU Eurozone

Eleven countries adopted the euro when it was launched in 1999, while six more countries have joined the bloc since then, most recently Estonia which joined at the beginning of 2011.

Austria Belgium Cyprus
Estonia Finland France
Germany Greece Ireland
Italy Luxembourg Malta
Netherlands Portugal Slovakia
Slovenia Spain

EU states obliged to join the Eurozone

Most of the European Union’s 27 member states still outside the euro are legally obliged to join the single currency when monetary conditions permit.

Sweden Latvia Lithuania
Czech Republic Hungary Romania
Poland Bulgaria

EU state with an opt-out on Eurozone participation

The exceptions are the UK and Denmark which have "opted out" of Eurozone membership.

Denmark United Kingdom

Source: Al Jazeera