Mazowsze (Mazowia) is an historical and ethnographic region in central Poland, straddling the Vistula River. The Mazovian Lowland is one of Poland's most extensive geographical regions. Its natural extension is the Podlassian Lowland at the confluence of the Narew and Biebrza Rivers and the basin of the middle Bug. As the two lowlands are difficult to separate, sometimes they are referred to as the Mazovian-Podlassian Lowland.

Historically, Mazowia is one of the oldest parts of Poland. Since the times of the first Polish prince, Duke Mieszko I, it was ruled by members of the Piast dynasty; in the 12th century an independent Mazowian principality came into being (many formidable Gothic castles and opulent churches that now dot Mazowia were built at that time) and in the 16th century all of Mazowia and Podlassia was incorporated into the Kingdom of Poland under Sigismundus I the Elder. Towns on major trade routes - Warsaw, Pultusk, Plock and Lomza - flourished. The centrally located Warsaw developed rapidly as a political, economic and cultural centre. In 1596 King Sigismund III Vasa made it his principal residence and thus Krakow ceased to be Poland's capital.