| Native Name: | |
| Conventional Long Name: | Duchy of Warsaw |
| Era: | High Middle Ages |
| Status: | Fiefdom within the Kingdom of Poland (1310–1320) Fiefdom of the United Kingdom of Poland (1320–1385) Fiefdom of the Crown of the Kingdom of Poland (1386–1488) |
| Government Type: | Feudal duchy |
| Life Span: | 1310–1370 1381–1488 |
| Event Start: | Partition of the Duchy of Masovia |
| Date Start: | 1310 |
| Event1: | Unification of the Duchy of Masovia |
| Date Event1: | 5 November 1370 |
| Event2: | Partition of the Duchy of Masovia |
| Date Event2: | June 1381 |
| Event End: | Incorporation into the Duchy of Czersk |
| Date End: | 1488 |
| P1: | Duchy of Masovia |
| Flag P1: | Chorągiew księcia mazowieckiego Siemowita.svg |
| Border P1: | no |
| S1: | Duchy of Masovia |
| Flag S1: | Chorągiew księcia mazowieckiego Siemowita.svg |
| Border S1: | no |
| S2: | Duchy of Czersk |
| Flag S2: | POL księstwo czerskie COA.svg |
| Border S2: | no |
| Religion: | Roman Catholic |
| Flag Type: | Banner |
| Flag Border: | no |
| Image Map Caption: | The map of the political division of Masovia between 1313 and 1345, including the Duchy of Warsaw. |
| Capital: | Warsaw |
| Official Languages: | Polish, Latin |
| Title Leader: | Duke |
| Leader1: | Siemowit II of Masovia |
| Year Leader1: | 1310–1313 (first of the first state) |
| Leader2: | Siemowit III |
| Year Leader2: | 1355–1370 (last of the second state) |
| Leader3: | Janusz I of Warsaw |
| Year Leader3: | 1381–1429 (first of the second state) |
| Leader4: | Bolesław V of Warsaw |
| Year Leader4: | 1471–1481 (last of the last state) |
The Duchy of Warsaw was a feudal district duchy in Masovia, centered on the Warsaw Land. Its capital was Warsaw.
The state was established in 1310, in the partition of the Duchy of Masovia, with duke Siemowit II of Masovia becoming its first leader.[1] It existed until 5 November 1370, when, under the rule of duke Siemowit III, duchies of Czersk, Rawa, and Warsaw were unified into the Duchy of Masovia.[2] [3] It was again re-established in June 1381, in the partition of the Duchy of Masovia, with duke Janusz I of Warsaw as its first leader.[4] [5] [6] It existed until 1488, when it got incorporated into the Duchy of Czersk.[7]
From 1310 to 1320, it was a fiefdom within the Kingdom of Poland, and from 1320 to 1385, a fiefdom of the United Kingdom of Poland, and from 1386 to 1488, a fiefdom of the Crown of the Kingdom of Poland.