Spanish Social Democratic Union (Spanish: Unión Social Demócrata Española; USDE) was a social liberal political party in Spain that opposed the Francoist State and wanted a liberal democracy in Spain. The USDE was founded in 1974 by Dionisio Ridruejo.
|Preceded by||Social Party of Democratic Action|
|National affiliation||Democratic Convergence Platform|
Social Democratic Federation
In 1975 the USDE joined the Democratic Convergence Platform. Fernando Chueca Goitia, one of the founders of USDE, left the party in July 1976 to join the People's Democratic Party, where he was elected president in December of that year.
- "Unión Social Demócrata Española". Fundación Juan March (in Spanish). Retrieved 13 February 2017.
- "El arquitecto Fernando Chueca". El País (in Spanish). 30 July 1976. Retrieved 13 February 2017.
- "Chueca Goitia, presidente del Partido Demócrata Popular". El País (in Spanish). 22 December 1976. Retrieved 13 February 2017.