The National Defence Council was the governing body in Republican Spain at the end of the Spanish Civil War (1936–1939). The council seized power with Colonel Segismundo Casado's coup on 5 March 1939 when it was clear that the Republicans had lost the war. The leaders hoped to negotiate an end to hostilities with the rebel forces led by General Francisco Franco. However, Franco insisted on unconditional surrender, and on 26 March 1939 launched the final offensive of the Spanish Civil War. By the end of the month he controlled the whole country. Most of the council members escaped into exile on British warships.

Spanish coup of March 1939, in historiography often referred to as Casado's coup, was a coup d'état organized in the Republican zone against the government of Juan Negrín. It was carried out by the military with support of the Anarchists and the Socialists; its leader was commander of the Army of the Centre, Segismundo Casado. The conspirators viewed the Negrín government as a hardly veiled Communist dictatorship. Most concluded that the government-endorsed strategy of unyielding resistance against the Nationalists would produce nothing but further deaths and sufferings while the war had already been lost. The military and some politicians intended the coup as a first step towards opening peace negotiations with the Nationalists; for the Anarchists and Socialists the priority was to remove the Communists from power.