The Schengen Agreement (English: SHENG-ən, Luxembourgish: [ˈʃæŋən] (listen)) is a treaty which led to the creation of Europe's Schengen Area, in which internal border checks have largely been abolished. It was signed on 14 June 1985, near the town of Schengen, Luxembourg, by five of the ten member states of the then European Economic Community. It proposed measures intended to gradually abolish border checks at the signatories' common borders, including reduced-speed vehicle checks which allowed vehicles to cross borders without stopping, allowing residents in border areas freedom to cross borders away from fixed checkpoints, and the harmonisation of visa policies.

In 1990, the Agreement was supplemented by the Schengen Convention which proposed the complete abolition of systematic internal border controls and a common visa policy. The Schengen Area operates very much like a single state for international travel purposes with external border controls for travellers entering and exiting the area, and common visas, but with no internal border controls. It currently consists of 27 European countries covering a population of over 400 million people and an area of 4,312,099 square kilometres (1,664,911 sq mi).

Originally, the Schengen treaties and the rules adopted under them operated independently from the European Union. However, in 1999 they were incorporated into European Union law by the Amsterdam Treaty, while providing opt-outs for the only two EU member states that had remained outside the Area: Ireland and the United Kingdom (which subsequently withdrew from the EU in 2020). Schengen is now a core part of EU law, and all EU member states without an opt-out which have not already joined the Schengen Area are legally obliged to do so when technical requirements have been met. Several non-EU countries are included in the area through special association agreements.