Yes it was. Full name was SFR Yugoslavia:
S-Socialist
F-Federative
R-Republic
Maribor, Socialist Republic of Slovenia, SFR Yugoslavia
Socialist Party of Yugoslavia was created in 1921.
Socialist Federal Republic of Yugoslavia ended in 1992.
Socialist Federal Republic of Yugoslavia was created in 1943.
Croatia was part of a socialist country called Yugoslavia until 1991 together with Slovenia, Bosnia, Serbia, Macedonia and Montenegro.
Yugoslavia is no longer a country. Before its breakup it was a Communist country.
Socialist Alliance of Working People of Yugoslavia ended in 1990.
The new country that was created as a south Slavic state was Yugoslavia. Yugoslavia consists of 6 Socialist Republics: Bosnia, Herzegovinia, Croatia, Macedonia, Montenegro, Slovenia, and Serbia.
Bosnia and Herzegovina and Croatia were formerly part of Yugoslavia (full name Socialist Federal Republic of Yugoslavia) until declaring independence in 1992.
Yugoslavia no longer exists but the country between historical Macedonia and Yugoslavia when it did exist would be the Socialist Republic of Macedonia, given autonomy and renamed from Vardar Banovina as part of a communist expansionist agenda to wrest historical Macedonia from Greece and forge for itself a strategic pathway to the Aegean for Yugoslavia.
Josip Broz Tito was the Prime Minister (1943-63) and later President (1953-80) of the Socialist Federal Republic of Yugoslavia
Maribor, Socialist Republic of Slovenia, SFR Yugoslavia