The Roman Catholic Archdiocese of Warmia (Latin: Archidioecesis Varmiensis, German: Bistum Ermland, former English: Archdiocese of Ermland, Archdiocese of the Ermeland) is an archdiocese of the Latin Rite of the Roman Catholic Church in present Poland. Originally erected as the Diocese of Ermland-Warmia in the 13th century, the diocese was originally a suffragan of the Archdiocese of Warsaw. Its first bishops were appointed by Polish and Teutonic Knights' officials and were mostly Germans. Under the Polish-Lithuanian Commonwealth the bishops were mostly Polish, but the faithful were in large majority ethnic Germans. Before the annexation of southern East Prussia by the People's Republic of Poland, the diocese of Ermland was led by Bishop Maximilian Kaller, the "Bishop of the Expellees". After 1946 it was claimed by the Polish Church, supported by the communist state's annexation of the area.
Only in 1992, was the diocese elevated to an Archdiocese and given two new suffragans, the Diocese of Ełk and the Diocese of Elbląg. The Diocese of Elk was created by merging territory from the then Diocese of Culm, (now Diocese of Pelplin); the then Diocese of Gdańsk, (now Archdiocese of Gdansk); and part of the Diocese of Warmia. The Diocese of Elblag was created from a subdivision of the Diocese of Warmia and the Diocese of Łomża.
The current Archdiocese contains a population of around 700,000 half of the former Diocese of Warmia. The Archepiscopal see is located in the city of Olsztyn.
The current Archbishop is Wojciech Ziemba, appointed by Pope Benedict XVI in 2006.