The Shatt al-Arab or Arvand Rud (Arabic: شط العرب, lit. 'River of the Arabs'; Persian: اروندرود, romanized: Arvand Rud, lit. 'Swift River') is a river of some 200 kilometres (120 mi) in length that is formed at the confluence of the Euphrates and Tigris rivers in the town of al-Qurnah in the Basra Governorate of southern Iraq. The southern end of the river constitutes the Iran–Iraq border down to its mouth, where it discharges into the Persian Gulf. The Shatt al-Arab varies in width from about 232 metres (761 ft) at Basra to 800 metres (2,600 ft) at its mouth. It is thought that the waterway formed relatively recently in geological time, with the Tigris and Euphrates originally emptying into the Persian Gulf via a channel further to the west. Kuwait's Bubiyan Island is part of the Shatt al-Arab delta.

The Karun, a tributary which joins the waterway from the Iranian side, deposits large amounts of silt into the river; this necessitates continuous dredging to keep it navigable.

The area used to hold the largest date palm forest in the world. In the mid-1970s, the region included 17–18 million date palms: an estimated one-fifth of the world's 90 million palm trees. However, by 2002, more than 14 million of the palms had been wiped out by combined factors of war, salt and pests; this count includes around 9 million palms in Iraq and 5 million in Iran. Many of the remaining 3–4 million trees are in poor health.