Segismundo Casado López (1893 – 18 December 1968) was a Spanish Army officer in the Second Spanish Republic during the Spanish Civil War, commanding the Republican Spanish Army in 1939.
Together with Julíán Besteiro, a member of the Cortes Generales and a socialist, in 1939 Casado conducted a coup d'état against the government of Prime Minister Juan Negrín, claiming Negrín wanted a Communist takeover.
Republican forces regained control of Madrid, and Casado's efforts to negotiate a peace with General Franco failed.
He insisted on unconditional surrender, which occurred in 1939.
Casado went into exile in Venezuela, not returning to Spain until 1961.