The parliamentary elections of 2015-16 in Greece, Spain and Portugal had extraordinary consequences, bringing repeat elections, unprecedented processes of government formation and uncharted government outcomes. Greece formed a coalition of radical left and radical right and Portugal its first government supported by the communist party while Spain took ten months to get a government. These developments are especially astonishing in three states which in previous decades were a byword for democratic stability. After the transitions following the fall of their dictatorships in the 1970s, Greece, Spain and Portugal established bipolar electoral competition and predictable patterns of government formation. But more recently, all three countries have been in the frontline of the economic crisis and austerity implementation, triggering electoral realignments and turning the radical left into a major player. This volume offers essential understanding of the political destabilisation of Southern Europe. It includes detailed analyses of all five ‘crisis elections’ and of Greece’s bailout referendum. It also provides studies of the five ‘new contender’ parties (SYRIZA, Podemos, Ciudadanos, the Bloco Esquerda and the Portuguese Communist Party) which played a key role in government formation for the first time. The chapters originally published as a special issue in South European Society and Politics.