The Nišava or Nishava (Bulgarian and Serbian Cyrillic: Нишава, Serbian pronunciation: [nǐʃaʋa]) is a river in Bulgaria and Serbia, a right tributary, and with a length of 218 km also the longest one, of the Južna Morava.

The Nišava originates in western Bulgaria, in the Stara Planina mountains (east of Kom Peak) near the village of Gintsi. Its source is close to the Serbian border. It enters Serbia after 67 km of flow through Bulgaria without receiving any major tributaries.

Because it flows through Gintsi, the upper course of the river is known as Ginska (Cyrillic: Гинска). It first flows to the south, then sharply turns west into the Godech Kettle, passing through Razboishte, after which it forms a gorge. Coming out of the gorge, it reaches Kalotina, a major border crossing on the Bulgarian-Serbian border (Kalotina-Gradina), and continues to the west into Serbia.

Flowing generally to the west for the remaining 151 km, it passes near Dimitrovgrad, Pirot, Bela Palanka, Niška Banja and Niš, one of the largest cities in Serbia, 10 km after which the Nišava empties into the Južna Morava. However, with the rapid growth of Niš in previous decades and its still fast growing suburbs, the banks of the Nišava are urbanized almost to its mouth.