The Jiu (Romanian: [ʒiw] ; Hungarian: Zsil [ʒil]; German: Schil or Schiel; Latin: Rabon) is a river in southern Romania. It is formed near Petroșani by the confluence of headwaters Jiul de Vest and Jiul de Est.

It flows southward through the Romanian counties Hunedoara, Gorj, Mehedinți and Dolj before flowing into the Danube near Zăval, a few kilometers upstream from the Bulgarian city of Oryahovo. It is 339 kilometres (211 mi) long, including its source river, Jiul de Vest. It has a basin of 10,430 km (4,030 sq mi). Its average discharge at the mouth is 97 m/s (3,400 cu ft/s).

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

The following towns are situated along the Jiu, from source to mouth: Petroșani (Jiul de Est), Lupeni (Jiul de Vest), Bumbești-Jiu, Târgu Jiu, Turceni, Filiași, and Craiova.

The following rivers are tributaries of the Jiu (from source to mouth):

• Left: Jiul de Est, Izvor, Polatiștea, Radul, Pârâul Alb, Păiușu, Chițiu, Sadu, Curpenoasa, Tetila, Iazu Topilelor, Hodinău, Amaradia (Gorj), Dâmbova, Cioiana, Gilort, Fratoștița, Cârnești, Răcari, Brădești, Amaradia (Dolj), Preajba, Lumaș, Leu, Gioroc
• Right: Jiul de Vest, Cândețu, Murga Mică, Murga Mare, Dumitra, Cerbănașu, Bratcu, Porcu, Sâmbotin, Cartiu, Pietroasa, Șușița (Gorj), Tismana, Timișeni, Jilț, Ceplea, Șușița (Mehedinți), Motru, Bâlta, Racovița, Argetoaia, Raznic, Tejac, Ulm, Prodila

• Jiu Valley