The Vistula (ˈvɪstjʊlə; Wisła, ˈvjiswa) is the longest river in Poland and the ninth-longest river in Europe, at in length. The drainage basin, reaching into three other nations, covers , of which is in Poland.
The Vistula rises at Barania Góra in the south of Poland, above sea level in the Silesian Beskids (western part of Carpathian Mountains), where it begins with the Little White Vistula (Biała Wisełka) and the Black Little Vistula (Czarna Wisełka).
It flows through Poland's largest cities, including Kraków, Sandomierz, Warsaw, Płock, Włocławek, Toruń, Bydgoszcz, Świecie, Grudziądz, Tczew and Gdańsk. It empties into the Vistula Lagoon (Zalew Wiślany) or directly into the Gdańsk Bay of the Baltic Sea with a delta of six main branches (Leniwka, Przekop, Śmiała Wisła, Martwa Wisła, Nogat and Szkarpawa).
The river is often associated with Polish culture, history and national identity. It is the country's most important waterway and natural symbol, and the term "Country upon Vistula" (kraj nad Wisłą) can be synonymous with Poland.
The name Vistula first appears in the written record of Pomponius Mela (3.33) in AD 40. Pliny in AD 77 in his Natural History names the river Vistla (4.81, 4.97, 4.100). The root of the name Vistula is often thought to come from Proto-Indo-European *weys-: 'to ooze, flow slowly' (cf. Sanskrit अवेषन् (avēṣan) "they flowed", Old Norse veisa "slime"), and similar elements appear in many European river-names (e.g. Svislach (Berezina), Svislach (Neman), Weser, Viešinta).
In writing about the river and its peoples, Ptolemy uses Greek spelling: Ouistoula. Other ancient sources spell the name Istula. Ammianus Marcellinus referred to the Bisula (Book 22) in the 380s. In the sixth century Jordanes (Getica 5 & 17) used Viscla.
The Anglo-Saxon poem Widsith refers to the Wistla. The 12th-century Polish chronicler Wincenty Kadłubek Latinised the river's name as Vandalus, a form presumably influenced by Lithuanian vanduõ 'water'.