Roman Catholicism in Croatia is part of the worldwide Catholic Church, under the spiritual leadership of the Pope

Pope

The Pope is the Bishop of Rome, a position that makes him the leader of the worldwide Catholic Church . In the Catholic Church, the Pope is regarded as the successor of Saint Peter, the Apostle...

 and curia

Curia

A curia in early Roman times was a subdivision of the people, i.e. more or less a tribe, and with a metonymy it came to mean also the meeting place where the tribe discussed its affairs...

 in Rome

Rome

Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...

.

There are an estimated 3.8 million baptised Roman Catholics in Croatia

Croatia

Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...

, roughly 85% of the population. The national sanctuary of Croatia is in Marija Bistrica

Marija Bistrica

Marija Bistrica is municipality in Krapina-Zagorje County in central Croatia, located on the slopes of the Medvednica mountain in Hrvatsko Zagorje, not far away from Zagreb...

. The patron of Croatia is Saint Joseph

Saint Joseph

Saint Joseph is a figure in the Gospels, the husband of the Virgin Mary and the earthly father of Jesus Christ ....

 since the Croatian Parliament declared him to be in 1687.
The Austrian Empire

Austrian Empire

The Austrian Empire was a modern era successor empire, which was centered on what is today's Austria and which officially lasted from 1804 to 1867. It was followed by the Empire of Austria-Hungary, whose proclamation was a diplomatic move that elevated Hungary's status within the Austrian Empire...

 signed a concordat

Concordat

A concordat is an agreement between the Holy See of the Catholic Church and a sovereign state on religious matters. Legally, they are international treaties. They often includes both recognition and privileges for the Catholic Church in a particular country...

 with the Holy See

Holy See

The Holy See is the episcopal jurisdiction of the Catholic Church in Rome, in which its Bishop is commonly known as the Pope. It is the preeminent episcopal see of the Catholic Church, forming the central government of the Church. As such, diplomatically, and in other spheres the Holy See acts and...

 in 1855 which regulated the Catholic Church within the empire.
In Yugoslavia, the Croatian bishops were part of the Bishops' Conference of Yugoslavia

Bishops' Conference of Yugoslavia

The Bishops' Conference of Yugoslavia was an episcopal conference of the Catholic Church covering the territory of Yugoslavia.The first such bishops' conference was held in the Kingdom of Serbs, Croats and Slovenes in November of 1918...

.

The Serbian Orthodox Church acted as a de-facto national church of the Kingdom of Yugoslavia.