The Duchy of Sandomierz is one of the territories created during the period of the fragmentation of Poland (early twelfth century).

It is originally part of the central Seniorate Province, inherited by Duke Henry of Sandomierz (see Testament of Boleslaw III Krzywousty).

The Duchy is located in the southeastern corner of the Kingdom of Poland, between the rivers of Pilica, Vistula, San, and Dunajec.

In the late Middle Ages, it becomes part of historic province of Lesser Poland, together with adjacent Duchy of Krakow.

In the early fourteenth century, the Duchy is turned into Sandomierz Voivodeship.

Its main urban centers are the historic towns of Sandomierz and Wislica.

Other main towns are Lublin, Radom, Checiny, Pilzno, Lukow and Stezyca.