Żuławy Wiślane (plural from "żuława", meaning fen), in English known as the Vistula Fens, is the alluvial delta area of the river Vistula, in the northern part of Poland. It is a flat and deforested region comprising wetlands and agricultural plains that cover approximately 1,700 squared kilometres, with much of the land being situated below sea level. Poland's lowest point (1.8 metres below sea level) is located at Raczki Elbląskie in the Żuławy region.
The area was largely reclaimed artificially by means of dykes, pumps, channels and an extensive drainage system. Its shape is similar to a reversed triangle formed by branching of Vistula into two separate rivers, Leniwka and Nogat at its height, confined by rivers themselves, and closed by the Vistula Lagoon at its base.