The Court of Justice of the European Communities, usually called the European Court of Justice (ECJ), is the highest court in the European Union (EU). It has the ultimate say on matters of EU law in order to ensure equal application across the various European Union member states.

The body was established in 1952 and is based in Luxembourg City — unlike most other Union institutions which are based in Brussels. The court is composed of one judge per member state although only 13 of them hear a case at any one time in the 'Grand Chamber'. The court is led by a president, since 2003 this has been Vassilios Skouris.

The court is assisted by a lower court, the Court of First Instance, dealing with certain issues. Two other courts deal with other responsibilities, the Civil Service Tribunal over employees of the Union's institutions and Court of Auditors (an institution in its own right) over the Union's accounts. It should not be confused with the European Court of Human Rights in Strasbourg, which is part of the Council of Europe.