| Native Name: | |
| Conventional Long Name: | Duchy of Gniezno |
| Era: | High Middle Ages |
| Status: | Fiefdom within the Duchy of Poland (1177–1227) Independent state (1227–1279) |
| Government Type: | feudal duchy |
| Year Start: | 1177 |
| Event Start: | Partition of the Duchy of Greater Poland |
| Event End: | Unification of the Duchy of Greater Poland |
| Year End: | 1279 |
| P1: | Duchy of Greater Poland |
| S1: | Duchy of Greater Poland |
| Religion: | Roman Catholic |
| Flag Border: | no |
| Image Map Caption: | Map of the Greater Poland with the political division. |
| Capital: | Gniezno |
| Title Leader: | Duke |
| Leader1: | Casimir II the Just |
| Year Leader1: | 1177–1181 (first) |
| Leader2: | Przemysł II |
| Year Leader2: | 1273–1279 (last) |
The Duchy of Gniezno was a feudal district duchy in the Greater Poland, centered on the Kalisz Region. Its capital was Gniezno. The state was established in 1177, in the partition of the Duchy of Greater Poland, after the rebellion against Mieszko III. Duke Casimir II the Just of the Piast dynasty become its first ruler.[1] It existed until 1279, when, it got united with duchies of Kalisz and Poznań, under the rule of Przemysł II, forming the Duchy of Greater Poland.[2] It remained a fiefdom within the Duchy of Poland, until 1227, and after that, it become an independent state.[3]