Even back before direct elections, the various parties of the alternative and radical left in the European Parliament worked together in a political group: the Communists and Allies Group.
This group carried on under this name until 1989 when four parties, the Italian CP; the United Left of Spain, the SPP of Denmark and Synaspismos of Greece decided to form a Group called the Gauche Unitaire Européenne (GUE). Its English name was European Unitarian Left, subsequently changed in 1992 to European United Left.
The remaining parties, PCF of France, PCP of Portugal, KKE of Greece were joined by one MEP from Workers' Party of Ireland to form the Coalition des Gauches / Left Unity Group.
In early 1993, the Italian CP, renamed the PDS, who had already joined the Socialist International in 1991, moved from GUE to join the Socialist Group in the European Parliament.
After the European Elections of June 1994, a process of gathering together all the forces of the non-social democratic left then began. This alliance, enlarged to include other parties, was established as a political group at the beginning of the fourth parliamentary term, under the name Confederal Group of the European United Left (GUE). The member parties were: United Left of Spain; the Communist Party of France; Communist Refoundation of Italy; the Communist Party of Portugal; the Communist Party of Greece; and Synaspismos of Greece.
The first president of the Group was Alonso Puerta a member of the Izquierda Unida of Spain.
Following enlargement of the EU to the Nordic countries and Austria in January 1995, the Group expanded to include: the Left Party (VP) of Sweden and the Left Alliance (Vas) of Finland. At the same time the Socialist Peoples' Party (SF) of Denmark rejoined the group and together with the Swedish and Finnish parties formed the Nordic Green Left (NGL) component within the group.
The group was renamed the Confederal Group of the European United Left/Nordic Green Left, with GUE/NGL as the standard acronym.
In 1998, Ken Coates a distinguished MEP, formerly in the British Labour Party, joined the GUE/NGL from the PES Group and Carlo Ripa Di Meana, an Italian MEP and former Environment Commissioner, joined the group from the Greens to bring the GUE/NGL to 34 MEPs from eight countries.
In the European elections of 1999, all the outgoing parties were successful in securing representation in the new Parliament. They were joined in the Group by the Party of Democratic Socialism (PDS) of Germany. The Group also welcomed a third party from Greece, the DIKKI, and five MEPs from France, elected on the LO-LCR list. Since Alonso Puerta did not contest the elections, a new President was elected: Francis Wurtz of the French Communist Party.
During the course of the 5th legislature, a total of 8 MEPs joned GUE/NGL from other groups: Ilka Schröder from the Green Group and Freddy Blak from the PES in 2001; Ole Krarup and Jens Okking from the EDD and Gérard Caudron, Michel Dary, Sami Nair, et Michel-Angel Scarbonchi from the PES in 2002. This brought the numbers up to 49 MEPs from ten countries, the GUE/NGL's highest ever representation in the European Parliament and made it the fourth largest Group.
In 2003, as part of the accession process of 10 new Member States, Observers joined the Group from Cyprus (2), Czech Republic (3), Latvia (1), and Slovakia (1), and these became full MEPs on 01 May 2004.
The European elections in June 2004 saw a solid electoral performance by GUE/NGL parties. Fourteen outgoing delegations were returned with 38 MEPs. With the addition of two new MEPs from Ireland's Sinn Féin, and one from the Left Bloc of Portugal, the Group had 41 Members from 14 Member States. Francis Wurtz was re-elected President of the Group.
Following the elections of June 2009, several new delegations joined the group, the Socialist Party from Ireland and the UC from Latvia. In France, the Front de Gauche Pour Changer d'Europe elected MEPs to the group from the Parti Communiste and the Parti de Gauche. The French delegation also included a member from the Parti Communiste Réunionnais. The new group consisted of 34 MEPs from 12 member states. On this occasion, Francis Wurtz who had been an MEP since 1979 did not go forward and the group elected in his place Lothar Bisky of the DIE.LINKE party from Germany.
Since March 15th 2012, Gabriele Zimmer of the DIE.LINKE party has been the group's president. She is the only female president of a political group at the European Parliament and was reelected as President after the 2014 elections which saw a 50% increase in the group's size to 52 MEPs. New parties were welcomed: Podemos (Spain), L'Altra Europa con Tsipras (Italy), an animal rights party from the Netherlands, an independent animal rights MEP from Germany, Bildu (Los Pueblos Deciden coalition, Basque country), Luke "Ming" Flanagan, an independent member from Ireland, and Barbara Spinelli, an independent Italian MEP. The group also regained its Finnish representative from the Vas party. The GUE/NGL's 26 women and 26 men make it the only group in Parliament where women and men are equally represented.