The Duchy of Brześć Kujawski,[a] also known as the Duchy of Kuyavian Brest, was a district principality in the Central Europe, in the region of Kuyavia.

It was formed on 3 January 1268 in the partition of the Duchy of Kuyavia.

Its first ruler was duke Władysław I Łokietek of the Piast dynasty.

[1][2] The state was conquered by the State of the Teutonic Order in 1332, during Polish–Teutonic War, with its capitol being captured on 21 April.

[3][4] Until 1300, it was an independent state, after what, it had become a fiefdom within the Kingdom of Poland, that in 1320, got transformed into the United Kingdom of Poland.