Duchy of Gniezno

The Duchy of Gniezno was a feudal district duchy in Greater Poland, with its territorial and administrative core in the Gniezno Land — the region surrounding the city of Gniezno. Its capital was Gniezno. The duchy was established in 1177, following the partition of the Duchy of Greater Poland after a rebellion against Mieszko III. Duke Casimir II the Just of the Piast dynasty became its first ruler.
Initially, Gniezno remained a fiefdom within the broader Duchy of Poland — a term commonly applied to the fragmented realm, which some sources continue to refer to as the Kingdom of Poland — until 1227, when Gniezno gained independence as a duchy. It existed in this form until 1279, when it was united with the duchies of Kalisz and Poznań under the rule of Przemysł II, forming a reconstituted Duchy of Greater Poland.