Jiu (Romanian pronunciation: [ʒiw], Latin: Rabon) is a river of southern Romania. It is formed near Petroşani by the junction of headwaters Jiul de Vest and Jiul de Est.

It flows southward through the Romanian counties Hunedoara, Gorj and Dolj before flowing into the Danube a few kilometers upstream from the Bulgarian city of Oryahovo, 339 kilometers from its sources. It has a basin of 10,080 km².

The upper Jiu Valley, around Petroşani and Lupeni, is Romania’s principal coal mining region.

Historically, the Jiu River was also called Rhabon by the Dacian people.

The following towns are situated along the river Jiu, from source to mouth: Petroşani (Jiul de Est), Lupeni (Jiul de Vest), Bumbeşti-Jiu, Târgu Jiu, Turceni, Filiaşi, Craiova

The following rivers are tributaries to the river Jiu:

Left: Jiul de Est, Izvorul, Polatiştea, Valea Radului, Pârâul Alb, Păiuşu, Chiţiu, Rafallo, Sadu, Curpenoasa, Bârcaciu, Tetila, Iazu Topilelor, Hodinău, Amaradia, Cioiana, Ceplea, Gilort, Ţânţăreni, Cârneşti, Brădeşti, Amaradia, Valea Fetii, Valea Şarpelui, Preajba, Lumaşu, Leu, Gioroc

Jiu or JIU may refer to :

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, tributary and rill. There are no official definitions for generic terms, such as river, as applied to geographic features, although in some countries or communities a stream may be defined by its size. Many names for small rivers are specific to geographic location; one example is "burn" in Scotland and northeast England. Sometimes a river is said to be larger than a creek, but this is not always the case, because of vagueness in the language.

Rivers are part of the hydrological cycle. Water within a river is generally collected from precipitation through a drainage basin from surface runoff and other sources such as groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (e.g., from glaciers). Potamology is the scientific study of rivers.