The Schengen Area incorporates 25 European countries into one block with no internal border controls for travellers. The Area includes three non-EU countries: Iceland, Norway and Switzerland. The Schengen rules were first adopted by the Schengen Agreement (1985) and absorbed into the European Union by the Amsterdam Treaty (1999). 

All EU Member States must adopt the Schengen rules, except for Ireland and the United Kingdom, which have opt outs. Bulgaria, Cyprus and Romania have not yet completed their adoption.