The Craiova Group (Quadrilateral), Craiova Four, or C4 is a cooperation project of four European states – Romania, Bulgaria, Greece and Serbia – for the purposes of furthering their European integration as well as economic, transport and energy cooperation with one another. The Group originated in a summit meeting of the heads of governments of Bulgaria, Romania and Serbia, held on 24 April 2015 in the Romanian city of Craiova. At the group's inaugural meeting, Romania's then-Prime Minister Victor Ponta indicated that he was inspired by the Visegrád Group. Romania and Bulgaria both joined the European Union in 2007, while Serbia has been in accession negotiations since 2014. Since 2017 meeting in Varna, Bulgaria and the inclusion of Greece, meetings have been quadrilateral.

One of the first initiatives, after a meeting in Vidin, Bulgaria, was to strengthen the telecommunication networks in the border areas of the countries. Other goals include helping Serbia join the European Union and the construction of a motorway linking Bucharest, Sofia and Belgrade.

On 2 November 2018, Prime Minister of Bulgaria Boyko Borisov stated that Prime Minister of Greece Alexis Tsipras proposed joint bid for the 2030 FIFA World Cup by Bulgaria, Romania, Serbia and Greece during the meeting in Thessaloniki.

Since the 2020s, however, the cooperation between the Craiova Group has stalled.