The Dunajec is a river running through northeastern Slovakia and southern Poland.It is also regarded as the main river of Goralscyzna. It is a right tributary of the Vistula River. It begins in Nowy Targ at the junction of two short mountain rivers, Czarny Dunajec and Biały Dunajec. Dunajec forms the border between Poland and Slovakia for 17 kilometers in the Pieniny Środkowe range, east of the Czorsztyn reservoir.
The Dunajec is 249 kilometers long, including its source river Czarny Dunajec, which makes it Poland's thirteenth longest river. It has a basin area of 6,796 square kilometres. On the Slovak/Polish border, it flows through the Zamagurie region, with attractions such as the Dunajec River Gorge, the Trzy Korony massif with a 500 metres precipice, Červený Kláštor, and two Pieniny castles in Czorsztyn and Niedzica.
Below the two source streams Dunajec flows through a broad valley called Nowotarska Basin. It then supplies the waters of the dam in Niedzica and the dam in Sromowce Wyżne.