The 1944 Bulgarian coup d'état, also known as the 9 September coup d'état, was a coup that overthrew the government of Kingdom of Bulgaria carried out on the eve of 9 September 1944. During the People's Republic of Bulgaria it was called using the propaganda term People's Uprising of 9 September – on the grounds of the broad unrest and Socialist Revolution – as it was a turning point politically and the beginning of radical reforms towards Soviet-style socialism.

The Tsardom of Bulgaria, also referred to as the Third Bulgarian Tsardom, sometimes translated in English as the "Kingdom of Bulgaria", or simply Bulgaria, was a constitutional monarchy in Southeastern Europe, which was established on 5 October 1908, when the Bulgarian state was raised from a principality to a tsardom.