The Metropolitan Archdiocese of Zagreb (Latin: Archidioecesis Metropolitae Zagrebiensis; Croatian: Zagrebačka nadbiskupija i metropolija) is the central Latin Church archdiocese of the Catholic Church in Croatia, centered in the capital city Zagreb.

The territory of the present-day Archdiocese of Zagreb was part of the Roman province of Pannonia Savia, centered around the busy river port of Sisak.

Bishop Castus was mentioned for the first time in 249 A.D. during Emperor Decius’s reign.

Ladislav then obtained approval for the foundation of the diocese from the Antipope Clement III.

[5] In 1227 Pope Gregory IX confirmed the grants and privileges of the Zagreb Diocese, among which the most important, the Felitianus' Charter from 1134 A.D., the oldest preserved document of Croatian land between the rivers Sava and Drava.