The Archdiocesan Archive of Gniezno was erected in 1960 by the Primate of Poland, card. Stefan Wyszyński. Its original stock had belonged earlier to the Metropolitan Cathedral Chapter in Gniezno. It is an archive of historical significance and its present collection is one of the largest and most valuable in Poland. Within the collection, among others, there are:
- Collection of more than 1500 legal documents – parchments and paper from the 11th – 20th cent.;
- Collection of more than 4500 Old Polish letters from the 15th-19th century.
- Several hundred volumes of acts from Metropolitan Cathedral Chapter (from15th-20th cent.), General Consistory (from 15th-20th cent.), Gniezno Seminary (from 17th-20th cent.);
- Primate of Poland acts (20th cent.);
- Acts of the Metropolitan Curia in Gniezno (20th cent.);
- Several thousand archival units from parishes and deaneries of our archdiocese (from 16th-20th century);
- Acts of convents that had existed in our archdiocese and were eliminated by Prussian partitioner in the 19th century;
- Personal acts and legacy of bishops and priests from the archdiocese (mainly 19th and 20th century);
- Over 300 seals and church stamps (from 17th-20th cent.);
- A rich cartographic collection (17th-20th cent.);
- Albums with photographs presenting bishops ministry and important liturgical events (19th & 20th cent.).
Among the exhibits there are many documents whose authors are popes, kings, primates of Poland, as well as superior Polish and foreign clergymen.
The oldest document kept in the Archive is the so called golden bull of Gniezno, the protective bull of pope Innocent II from the year 1136, written in Latin, in which there are over 400 personal names and names of places in the Polish language. This is also the oldest relic in Polish language.