The San is a river in southeastern Poland and western Ukraine. It is a tributary of the river Vistula. With a length of 458 kilometres (285 mi), the San is the 6th-longest Polish river. It has a basin area of 16,877 km2, of which 14,426 km2 is in Poland.

The Vistula is the longest river in Poland and the ninth-longest in Europe, at 1,047 kilometres in length. Its drainage basin, extending into three other countries apart from Poland, covers 193,960 km2 (74,890 sq mi), of which 168,868 km2 (65,200 sq mi) is in Poland.