The Indus IN-dəs (Sanskrit: Sindhu) is a transboundary river of Asia and a trans-Himalayan river of South and Central Asia. The 3,120 km (1,940 mi) river rises in mountain springs northeast of Mount Kailash in Western Tibet, flows northwest through the disputed region of Kashmir, bends sharply to the left after the Nanga Parbat massif, and flows south-by-southwest through Pakistan, before emptying into the Arabian Sea near the port city of Karachi.

The river has a total drainage area of circa 1,120,000 km² (430,000 sq mi). Its estimated annual flow is around 243 km³ (58 cu mi), making it one of the 50 largest rivers in the world in terms of average annual flow. Its left-bank tributary in Ladakh is the Zanskar River, and its left-bank tributary in the plains is the Panjnad River which is formed by the successive confluences of the five Punjab rivers, namely the Chenab, Jhelum, Ravi, Beas, and Sutlej rivers. Its principal right-bank tributaries are the Shyok, Gilgit, Kabul, Kurram, and Gomal rivers. Beginning in a mountain spring and fed with glaciers and rivers in the Himalayan, Karakoram, and Hindu Kush ranges, the river supports the ecosystems of temperate forests, plains, and arid countryside.

The northern part of the Indus Valley, with its tributaries, forms the Punjab region of South Asia, while the lower course of the river ends in a large delta in the southern Sindh province of Pakistan. The river has historically been important to many cultures of the region. The 3rd millennium BCE saw the rise of Indus Valley Civilisation, a major urban civilization of the Bronze Age. During the 2nd millennium BCE, the Punjab region was mentioned in the Rigveda hymns as Sapta Sindhu and in the Avesta religious texts as Saptha Hindu (both terms meaning "seven rivers"). Early historical kingdoms that arose in the Indus Valley include Gandhāra, and the Ror dynasty of Sauvīra. The Indus River came into the knowledge of the Western world early in the classical period, when King Darius of Persia sent his Greek subject Scylax of Caryanda to explore the river, c. 515 BCE.