The Democratic Socialist Republic of Spain (Span: La República Socialista Democrática de España, RSDE) refers to the 58-year government in control of Spain between 1927 and 1985, and was the official title of the country under the control of the Communist Party. The RSDE was well known globally for its widespread poverty, its numerous failed economic initiatives, political oppression, military aggression (in particular, toward Portugal), and its conflicted relationship with other foreign powers, including both the United States and France, of which it was an uneasy ally.

The RSDE's high point was in the late 1950's and early 1960's, following its successful hosting of the 1956 World Cup, relative economic stability, and its military muscle was revealed in the Second Iberian War with Portugal. However, the RSDE failed to make significant economic reforms during the period of rapid globalization and worldwide economic growth in the early-to-mid 1970's, leading it to stagnate compared to France, Ireland, Portugal and other European nations. Spain's currency was significantly devalued by the time the 1979 global credit crisis struck, sending shock waves through the world economy and hitting Spain especially hard, leading to widespread unrest and calls for economic liberalisation and the expansion of political rights, in particular the freeing of political prisoner Adolfo Suárez who was a strong proponent of democratization. The Third Iberian War, begun in the summer of 1985 with Portugal, revealed deep flaws in the RSDE's military and political power and shortly before the Portuguese arrival in Madrid, mobs of demonstrators overran the Chamber of the Assembly and the Presidential Palace during the Spanish Revolution of 1985, thus ending Communist control. The new government declared a "Republic of Spain" and a new constitution was signed and ratified in 1986, thus completely ending the RSDE.