The term Schengen Agreement is used for two agreements concluded between European states in 1985 and 1990 which deal with the abolition of systematic border controls between the participating countries. By the Treaty of Amsterdam, the two agreements themselves and all decisions that have been enacted on their basis have been incorporated into the law of the European Union. This body of legal provisions is referred to as the Schengen Acquis. The Schengen Acquis had been legally defined by the 176/l_17619990710en00010016.pdf" target="_blank">Council Decision of 20 May 1999 concerning the definition of the Schengen acquis for the purpose of determining, in conformity with the relevant provisions of the Treaty establishing the European Community and the Treaty on European Union, the legal basis for each of the provisions or decisions which constitute the acquis (1999/435/EC). Subsequent amendments to that acquis, including the Schengen Agreements themselves, have been made in the form of European Union regulations. The main purpose of the establishment of the Schengen rules is the abolition of physical borders among European countries.

The Schengen rules apply among most European countries, covering a population of over 400 million and a total area of . They include provisions on common _policy on the temporary entry of persons (including the Schengen Visa), the harmonisation of external border controls, which are coordinated by the Frontex agency of the European Union, and cross-border police and judicial co-operation.

A total of 31 states, including 27 European Union states and four non-EU members (Iceland, Norway, Liechtenstein and Switzerland), are subject to all or some of the Schengen rules, and 24 have fully implemented them so far. Ireland and the United Kingdom did not sign up to the original Schengen Convention of 1990 and retained a right to opt out of the application of the rules after their conversion into European Union law. Thus, they have not ended border controls with other EU Member States, but take part in the measures relating to police and judicial co-operation which form part of the Schengen acquis.

Border posts and checks have been removed between the states which form the Schengen area. A common Schengen visa allows tourists or other visitors access to the area. Holders of residence permits to a Schengen state enjoy the freedom of travel to other Schengen states for a period of up to three months.