Harappa (Punjabi pronunciation: [ɦəɽəˈpaː]) is an archaeological site in Punjab, Pakistan, about 24 kilometres (15 miles) west of Sahiwal, that takes its name from a modern village near the former course of the Ravi River. The Ravi now runs eight kilometres (five miles) to the north.

The city of Harappa is believed to have had as many as 23,500 residents and occupied about 150 hectares (370 acres) with clay brick houses at its greatest extent during the Mature Harappan phase (2600 BC – 1900 BC), which is considered large for its time.

The ancient city of Harappa was heavily damaged under British rule when bricks from the ruins were used as track ballast to construct the Lahore–Multan Railway. The current village of Harappa is less than one kilometre (5⁄8 mi) from the ancient site. Although modern Harappa has a legacy railway station from the Raj period, it is a small crossroads town of 15,000 people today. In 2004, the site was added to the tentative list for UNESCO World Heritage Sites. In 2005, a controversial amusement park scheme at the site was abandoned when builders unearthed many archaeological artefacts during the early stages of building work.

The Harappan Civilization has its earliest roots in cultures such as that of Mehrgarh, approximately 6000 BC. The two greatest cities, Mohenjo-daro and Harappa, emerged c. 2600 BC along the Indus River valley in Punjab and Sindh. The civilization, with a possible writing system, urban centres, drainage infrastructure and diversified social and economic system, was rediscovered in the 1920s also after excavations at Mohenjo-daro in Sindh near Larkana, and Harappan cities, in west Punjab south of Lahore. A number of other sites stretching from the Himalayan foothills in the East Punjab, to Gujarat in the southeast, and Balochistan, Pakistan in the southwest, have also been discovered and studied. Although the archaeological site at Harappa was damaged in 1857 when engineers constructing the Lahore-Multan railway used bricks from the ruins for track ballast, an abundance of artefacts has nevertheless been recovered.

Due to falling sea-levels, certain regions were abandoned during the late Harappan period. In its later stages, the Harappan civilization lost features such as writing and hydraulic engineering. As a result, the Ganges Valley settlement gained prominence and Ganges' cities developed.

The earliest recognisably Harappan sites date to 3500 BC. This early phase lasts till around 2600 BC. The civilization's mature phase lasted from 2600 BC to 2000 BC. This is when the great cities were at their height. Then, from around 2000 BC, there was a steady disintegration that lasted till 1400 BC – what is usually called Late Harappan. There is no sign that the Harappan cities were laid waste by invaders. The evidence strongly points to natural causes. A number of studies show that the area which is today the Thar Desert was once far wetter and that the climate gradually became drier.

The Indus Valley civilization was basically an urban culture sustained by surplus agricultural production and commerce, the latter including trade with Elam and Sumer in southern Mesopotamia. Both Mohenjo-daro and Harappa are generally characterised as having "differentiated living quarters, flat-roofed brick houses, and fortified administrative or religious centers." Although such similarities have given rise to arguments for the existence of a standardised system of urban layout and planning, the similarities are largely due to the presence of a semi-orthogonal type of civic layout, and a comparison of the layouts of Mohenjo-Daro and Harappa shows that they are in fact, arranged in a quite dissimilar fashion.

The weights and measures of the Indus Valley Civilisation, on the other hand, were highly standardised, and conformed to a set scale of gradations. Distinctive seals were used, among other applications, perhaps for the identification of property and shipment of goods. Although copper and bronze were in use, iron was not yet employed. "Cotton was woven and dyed for clothing; wheat, rice, and a variety of vegetables and fruits were cultivated; and a number of animals, including the humped bull, was domesticated," as well as "fowl for fighting". Wheel-made pottery—some of it adorned with animal and geometric motifs—has been found in profusion at all the major Indus sites. A centralised administration for each city, though not the whole civilisation, has been inferred from the revealed cultural uniformity; however, it remains uncertain whether authority lay with a commercial oligarchy. Harappans had many trade routes along the Indus River that went as far as the Persian Gulf, Mesopotamia, and Egypt. Some of the most valuable things traded were carnelian and lapis lazuli.