European Territorial Cooperation (CTE or ETC), better known as Interreg, is a European regional development financing instrument.

Interreg has been designed within the framework of the European Cohesion Policy to intensify institutional cross-border cooperation between regions located on the internal and external borders of the European Union, and regions within transnational areas. As regions of EU Member States face similar issues not contained by borders, territorial cooperation stands out as a key tool in effectively addressing socio-economic and environmental challenges. Beyond the objective of European Territorial Cooperation (ETC) is to undermine the influence of national borders to promote a harmonious economic, social and cultural development of the Union globally.[1]​.

Interreg is built around three strands of cooperation: cross-border (Interreg A), transnational (Interreg B) and interregional (Interreg C). The current programming period 2014-2020 covers all 28 EU Member States, three participating EFTA countries (Norway, Switzerland, Lichtenstein), 6 accession countries and 18 neighboring countries. The total allocation of Interreg V derived from the European Regional Development Fund is 10.1 billion euros, which represents 2.8% of the total European Cohesion Policy budget.[2]​.