The Democratic Center Union (Spanish: Unión de Centro Democrático, UCD) was a political coalition formed by several groups of conservatives, "democristians ", liberals and social democrats in Spain in 1977.

It was at first led by Adolfo Suárez which constituted the framework of the government through the Spanish transition from dictatorship to democracy. The reform group from the Franco regime also joined and Suárez was elected the coalition president. The group won the general elections in June the same year, and Suárez became the first democratically elected Prime Minister of Spain after the Franco regime. He later united all fragments into one common party (with the same name).

The party followed with another victory in the 1979 elections, but the diverse ideological beliefs and too many strong leaders soon led to a crisis within the party. Suárez resigned in 1981 and was followed by Leopoldo Calvo Sotelo who became the new Prime Minister. Augustín Rodríguez Sahagún became the party leader. Soon there after, Calvo Sotelo took over as the head of the party and then giving the title to Landelino Lavilla in 1982.

The crisis led to a separation of the different groups. First the "democristians" left the party, then the social democrats and finally Suárez himself. He formed his own party, Democratic and Social Center which never achieved the success of UCD. In the 1982 elections The Democratic Center Union only got 7,14% of the votes and consecuently lost. The year after the party dissolved and disappeared from Spanish politics forever.

See also: Politics of Spain