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The Indus Valley Civilisation (IVC), also known as the Indus Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 BCE to 1300 BCE, and in its mature form 2600 BCE to 1900 BCE. Together with ancient Egypt and Mesopotamia, it was one of three early civilisations of the Near East and South Asia, and of the three, the most widespread. Its sites spanned an area from much of Pakistan, to northeast Afghanistan, and northwestern India. The civilisation flourished both in the alluvial plain of the Indus River, which flows through the length of Pakistan, and along a system of perennial monsoon-fed rivers that once coursed in the vicinity of the Ghaggar-Hakra, a seasonal river in northwest India and eastern Pakistan.

The term Harappan is sometimes applied to the Indus civilisation after its type site Harappa, the first to be excavated early in the 20th century in what was then the Punjab province of British India and is now Punjab, Pakistan. The discovery of Harappa and soon afterwards Mohenjo-daro was the culmination of work that had begun after the founding of the Archaeological Survey of India in the British Raj in 1861. There were earlier and later cultures called Early Harappan and Late Harappan in the same area. The early Harappan cultures were populated from Neolithic cultures, the earliest and best-known of which is Mehrgarh, in Balochistan, Pakistan. Harappan civilisation is sometimes called Mature Harappan to distinguish it from the earlier cultures.

The cities of the ancient Indus were noted for their urban planning, baked brick houses, elaborate drainage systems, water supply systems, clusters of large non-residential buildings, and techniques of handicraft and metallurgy. Mohenjo-daro and Harappa very likely grew to contain between 30,000 and 60,000 individuals, and the civilisation may have contained between one and five million individuals during its florescence. A gradual drying of the region during the 3rd millennium BCE may have been the initial stimulus for its urbanisation. Eventually it also reduced the water supply enough to cause the civilisation's demise and to disperse its population to the east.

Although over a thousand Mature Harappan sites have been reported and nearly a hundred excavated, there are five major urban centres: Mohenjo-daro in the lower Indus Valley (declared a UNESCO World Heritage Site in 1980 as "Archaeological Ruins at Moenjodaro"), Harappa in the western Punjab region, Ganeriwala in the Cholistan Desert, Dholavira in western Gujarat (declared a UNESCO World Heritage Site in 2021 as "Dholavira: A Harappan City"), and Rakhigarhi in Haryana. The Harappan language is not directly attested, and its affiliation uncertain as the Indus script has remained undeciphered.[18] A relationship with the Dravidian or Elamo-Dravidian language family is favoured by a section of scholars.

Indus Valley Civilization at its peak had a population between one and five million people.