The Metropolitan Archdiocese of Gniezno was established in 1000 AD on the initiative of the Polish duke Bolesław I the Brave.

He had the relics of the missionary and martyr Adalbert of Prague (Wojciech) transferred to Gniezno Cathedral, which soon became a major pilgrimage site.

Led by Adalbert's half-brother Radim Gaudentius, the ecclesiastical province then comprised the suffragan dioceses in Kraków, Wrocław, and Kołobrzeg (extinct in 1015), and from about 1075 also Poznań.

When on 16 July 1821 the Diocese of Wrocław was put under direct authority of the Holy See by Pope Pius VII, Gniezno was affiliated in personal union (aeque principaliter) with the Archdiocese of Poznań.

By Apostolic constitution of 25 March 1992, Pope John Paul II again divided the union between the archdioceses of Gniezno and Warsaw.