Longest River in South Asia

Short answer

• On the most commonly cited set of figures, the longest river in South Asia is the Indus River, at about 3,200 kilometers, or about 2,000 miles, according to Encyclopaedia Britannica.
• The Indus rises in southwestern Tibet, in China, near Lake Mapam, flows through the Kashmir region, then turns south through Pakistan, and reaches the Arabian Sea through a delta south and southeast of Karachi.
• The closest contender is the Brahmaputra River, which Britannica gives as about 2,900 kilometers, or about 1,800 miles. It rises in Tibet as the Yarlung Tsangpo, flows through India, then through Bangladesh as the Jamuna, and joins the Ganges system on its way to the Bay of Bengal.
• The Ganges River comes next among the great rivers of the region, at 2,510 kilometers, or 1,560 miles, according to Britannica. It flows through India and Bangladesh to the Bay of Bengal.
• The honest short answer therefore has two parts. First, the Indus is the longest river in South Asia when rivers are compared on one consistent set of published figures, with Britannica as the reference used here. Second, river lengths are not exact constants. Different sources give different lengths for the same river, because they choose different source points, different mouth points, and different ways of measuring a winding channel. No single length for the Indus should be quoted without naming its source.
• Do not confuse longest with largest. Largest can mean greatest discharge, widest basin, or greatest volume of water. Longest means greatest length from source to mouth. The Ganges and Brahmaputra system carries an enormous volume of water, but that does not make either river longer than the Indus on the figures used here.

Why This Answer Needs a Qualifier

A river length looks like a simple fact, like the height of a mountain. In practice it depends on choices, and different choices give different answers. Four choices matter most.

First, where does the river start? A system has many headwater streams, and choosing one glacier, lake outlet, or spring over another can add or remove tens or even hundreds of kilometers. For the Indus, Britannica places the rise near Lake Mapam in southwestern Tibet, at about 5,500 meters. Other accounts choose a different headwater stream in the same high country, and the length changes with that choice.

Second, where does the river end? A river that reaches the sea through a delta has several distributaries, and the delta shifts over time. Measuring to one mouth rather than another changes the total. In a braided river, where the channel splits and rejoins around islands, the choice of channel also changes the total.

Third, how is the winding channel measured? A measurement from a small scale map smooths out bends and gives a shorter length. A measurement from detailed satellite imagery follows more bends and gives a longer length. Both can be honest, and they will disagree.

Fourth, does the measurement count a tributary as part of the main river? In some systems, the longest continuous watercourse is measured by following the longest tributary upstream, even when tradition gives the main river a different name above the confluence. That method can give a longer figure for the same named river.

This article therefore does not present one unqualified length as settled truth. It ranks rivers on one consistent source, Britannica, and then shows where other sources differ. A short exam answer can use the Indus at about 3,200 kilometers, with Britannica as the source. A careful answer should add that other sources give lower or higher figures for both the Indus and the Brahmaputra.

The Ranking on One Consistent Set of Figures

Comparing rivers fairly means using the same kind of measurement for each river, as far as possible. Mixing one source for the Indus, another source for the Brahmaputra, and a third source for the Ganges can create a false ranking, because each source may have measured differently. The table below therefore uses Britannica figures for all three leading rivers. The Amu Darya is included because it touches Afghanistan, which is often counted as part of South Asia, and because it appears in some lists of South Asian rivers. Its length is given from Britannica Kids, a Britannica publication, so that the comparison stays within one publishing family.

River	Length given by Britannica	Main course in brief
Indus	About 3,200 kilometers (about 2,000 miles)	Tibet, Kashmir region, Pakistan, to the Arabian Sea
Brahmaputra	About 2,900 kilometers (about 1,800 miles)	Tibet, India, Bangladesh, joining the Ganges system to the Bay of Bengal
Ganges	2,510 kilometers (1,560 miles)	India and Bangladesh, to the Bay of Bengal
Amu Darya	2,540 kilometers (1,578 miles)	Central Asia, touching Afghanistan, to the Aral Sea region

On this consistent set, the Indus leads the Brahmaputra by about 300 kilometers. That lead is real on these figures, but it is not large enough to survive every alternative measurement. The section on why lengths disagree explains why, and why that fact should be stated rather than hidden.

What Counts as a River in South Asia

South Asia is commonly understood to include Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka. Rivers do not respect that list neatly. The Indus and the Brahmaputra both rise in Tibet, outside South Asia, and then flow through South Asia for most of their courses. The question “longest river in South Asia” is normally understood to mean the longest river associated with South Asia, measured over its full course, not only the part inside the political region. This article uses that common meaning.

If the question meant only the segment inside South Asia, a different calculation would be needed. If it meant only rivers that rise and end inside South Asia, the Indus and the Brahmaputra would both be excluded by their Tibetan headwaters, and the Ganges, which rises in India and ends in Bangladesh, would become the leading candidate. Neither is the question most readers are asking, but both show why the scope should be stated.

A related point concerns river systems. The Ganges, the Brahmaputra, and the Meghna join in Bangladesh to form one of the great river systems of the world, with the third greatest average discharge of the world’s rivers according to Britannica. That combined system is not one river, so this article does not count it as a single river.

The Indus: From Source to Sea

Britannica describes the Indus as a great trans-Himalayan river of South Asia, with a total drainage area of about 1,165,000 square kilometers. Its course runs from high mountain headwaters, through deep gorges, to foothill and plain tributaries, and then to a low delta.

The river rises in the southwestern Tibet Autonomous Region of China near Lake Mapam, at about 5,500 meters. For about 320 kilometers it flows northwest, crossing the southeastern boundary of the disputed Kashmir region at about 4,600 meters. A short way beyond Leh, in the Indian administered union territory of Ladakh, it is joined on its left by its first major tributary, the Zanskar River. Continuing into the Pakistani administered areas of the Kashmir region, it is joined by the Shyok River on the right bank. Below that confluence, it is fed by glaciers on the Karakoram Range, the Nanga Parbat massif, and the Kohistan highlands.

The Shigar River joins on the right bank near Skardu in Baltistan, the Gilgit River joins at Bunji, and the Astor River joins as a left bank tributary. The Indus then flows west and turns south and southwest to enter Khyber Pakhtunkhwa province, skirting the Nanga Parbat massif in gorges 4,600 to 5,200 meters deep. It then flows as a rapid mountain stream to the reservoir of Tarbela Dam. The Kabul River joins just above Attock, at about 600 meters, and the river then cuts across the Salt Range near Kalabagh to enter the Punjab Plain.

On the plain, the Indus becomes much larger, and during the flood season, from July to September, it is several miles wide. It flows through western and southern Punjab province at about 80 meters. Because it moves slowly, it deposits silt that raises its bed above the surrounding plain, and most of the plain in Sindh has been built up by Indus alluvium. Embankments prevent most flooding, but they occasionally give way, as in floods recorded by Britannica in 1947, 1958, and 2010.

Near Thatta the Indus branches into distributaries that form a delta and join the sea at various points south and southeast of Karachi. The delta covers 7,800 square kilometers or more, and extends about 210 kilometers along the coast. That shifting mouth is one reason why a single precise length is hard to fix.

The Tributaries That Make the Indus System

A river ranking based on the main stem alone can hide how much of the Indus system is carried by its tributaries. The most important group comes from the eastern Punjab Plain. These five rivers, the Jhelum, Chenab, Ravi, Beas, and Sutlej, give the name Punjab, meaning Five Rivers, to the region divided between Pakistan and India. They join the Indus system from the east and greatly increase its flow on the plain.

In the mountains, the tributary pattern is different. The Zanskar, Shyok, Shigar, Gilgit, and Astor rivers drain high glacier country and bring meltwater into the main stem. The Kabul River, joining just above Attock, drains a large catchment to the west, including much of eastern Afghanistan. Taken together, these tributaries explain why the Indus can rise as a high mountain stream and end as a great plain river: it collects water from the Himalayas, the Karakoram Range, the Hindu Kush, and the Punjab Plain along a single course. The tributaries also explain the political importance of the river, because the Indus system crosses several countries and administered regions, so no single government controls its whole catchment.

The Closest Contender: The Brahmaputra

The Brahmaputra is the river most likely to be confused with the Indus in a longest river list. It is long, it rises in the same high country, and some compilations give it a length close to or even above some compilations of the Indus.

Britannica’s summary describes it as a river of Central and South Asia. From its headsprings in the Tibet Autonomous Region of China, as the Yarlung River, it flows across southern Tibet to break through the Himalayas in great gorges, where it is known as the Dihang. It flows southwest through the Assam Valley and south through Bangladesh, where it is known as the Jamuna. There it merges with the Ganges to form a vast delta. Britannica gives its length as about 1,800 miles, or 2,900 kilometers, and notes its importance for irrigation and transportation.

In Bangladesh it becomes the Jamuna, a wide braided river that shifts channels, builds and erodes islands, and floods large areas in the monsoon season. That braided character, like the Indus delta, makes precise measurement difficult. The Brahmaputra also carries a large volume of water and sediment, which renews floodplain soils and creates flood risk. A river can therefore be second in length and still be first in importance for a particular valley or season.

Why Published Lengths Disagree

The disagreement between sources for the Indus and the Brahmaputra is not a sign that one source is inventing numbers. It shows that river length measurement has no single standard method. Three examples make the pattern clear.

First, Britannica’s own history shows the shift. Its main Indus article now gives some 2,000 miles, or 3,200 kilometers. Its shorter summary entry has given a lower figure, 1,800 miles, or 2,900 kilometers, in the past. A reader who quotes “Britannica” without saying which entry, and when it was updated, can therefore quote two different lengths from the same publisher. This article uses the main Indus article figure, updated in 2026, and says so, so a reader can check it.

Second, other modern compilations give the Indus as 3,180 kilometers, close to the Britannica main figure, and also give a shorter figure of 2,880 kilometers that has been widely used. The shorter figure is essentially the same as the Britannica figure for the Brahmaputra. If one compilation uses the short Indus figure and a long Brahmaputra figure, the ranking can appear to reverse. The ranking here holds on the consistent Britannica set, and it would need to be rechecked, not assumed, on any other set.

Third, an extended figure of about 3,600 kilometers for the Indus was announced by a Chinese research group in 2011, based on satellite remeasurement and an alternative source point. That figure has been reported in reference summaries, but detailed analysis has not been published in a form that would allow other researchers to reproduce it in full. This article therefore records it as a reported claim, not as a verified length, and does not use it for the ranking.

The same logic applies to the Brahmaputra, given as 2,880 kilometers in some compilations, about 3,000 kilometers in others, and 3,080 kilometers when a longer upstream course is counted. The safe reading is a range, about 2,900 to 3,100 kilometers, rather than a single exact number. When a website gives a river length, ask which source it is from, which source and mouth points were used, and whether the same method was used for every river in the list. If those questions cannot be answered, treat the ranking as approximate, even if the numbers look precise.

The Ganges and the Amu Darya in the Same List

The Ganges is third among the great rivers considered here, but third in length does not mean third in cultural or human importance. Britannica gives the Ganges as 1,560 miles, or 2,510 kilometers, and describes it as the holy river of Hinduism, flowing through one of the most fertile and densely populated regions in the world. It rises in the southern Great Himalayas, with five headstreams in northern Uttarakhand state, of which the Alaknanda and the Bhagirathi are the two main headstreams. They unite at Devaprayag to form the Ganga, which flows onto the Indo-Gangetic Plain at Haridwar, then south and east through Uttar Pradesh, Bihar, and West Bengal, receiving the Yamuna and many Himalayan tributaries from Nepal, before entering Bangladesh, where it is called the Padma, joining the Brahmaputra, and reaching the Bay of Bengal through the Ganges delta. Its basin supports hundreds of millions of people and drains one fourth of the territory of India according to Britannica.

The Amu Darya is included for completeness, because Afghanistan is often counted in South Asia and the Amu Darya forms part of Afghanistan’s northern border. Britannica Kids gives it as 1,578 miles, or 2,540 kilometers, from headwaters in the eastern Pamir Mountains in Afghanistan to the southern shore of the Aral Sea in Uzbekistan. On that figure it is slightly longer than the Ganges, but still well short of the Indus and the Brahmaputra. Other rivers in South Asia, such as the Yamuna, Godavari, Krishna, Narmada, and Helmand, are important in their own basins, but none approaches the top three in total length on the figures used here.

Why the Indus Matters Beyond Its Length

Length is the question, but it is not the whole story. The Indus has shaped settlement, farming, and politics for thousands of years.

First, ancient civilization. Britannica notes that the Indus civilization, also called the Harappan civilization, developed in the Indus River valley during the 3rd millennium BCE, with large cities such as Harappa and Mohenjo-daro and more than 100 towns and villages. The river gave its name, through the Sanskrit Sindhu, to the country name India, as Britannica records for the Rigveda hymns composed about 1500 BCE.

Second, farming. Since ancient times, agriculture in the Indus valley has relied on irrigation from the river. Britannica records that modern irrigation engineering began around 1850, leading to large canal systems, and that by 1947 this had become the world’s greatest canal irrigation system. The system still waters much of Punjab and Sindh, so a change in flow, from drought, flood, or upstream use, has immediate human consequences.

Third, the Indus Waters Treaty of 1960. The World Bank’s fact sheet records that it was signed in 1960 after nine years of negotiations between India and Pakistan with the help of the World Bank, which is also a signatory. It allocates the western rivers, the Indus, Jhelum, and Chenab, to Pakistan, and the eastern rivers, the Ravi, Beas, and Sutlej, to India, while allowing each country certain uses on the rivers allocated to the other. It sets up the Permanent Indus Commission and procedures for questions, differences, and disputes, with a limited procedural role for the World Bank after signing. According to the World Bank, it has survived frequent tensions, including conflict, and has provided a framework for irrigation and hydropower development for more than half a century.

Fourth, energy, flood risk, and ecology. Tarbela Dam on the Indus and Mangla Dam on the Jhelum generate hydroelectricity, according to Britannica, while the flood season can destroy embankments and flood large areas, as in 2010. Near the mouth, for about 240 kilometers along the coast, there are creeks and shallow seawater rich in marine fish, with pomfrets and prawns among the most important catches. Managing the Indus therefore means managing both scarcity and excess, and protecting a delta sensitive to reduced freshwater flow.

How to Answer the Question in Different Settings

For a short quiz, write: The Indus River, about 3,200 kilometers according to Encyclopaedia Britannica, is the longest river in South Asia. That answer is correct on the stated source, and it names the source.

For a school essay, add the qualifier: River lengths vary by source and method. On a consistent Britannica set, the Indus leads the Brahmaputra by about 300 kilometers, and the Ganges is third at 2,510 kilometers.

For a research note, add the range: Britannica’s main Indus article gives some 2,000 miles, or 3,200 kilometers, while other compilations give 2,880 kilometers or 3,180 kilometers, and a reported 2011 remeasurement gave about 3,600 kilometers without full published detail. The Brahmaputra ranges to about 3,080 kilometers in some compilations. Report the ranking as holding on the stated set, not as an absolute fact independent of measurement.

For a map exercise, trace the courses: Tibet to Kashmir to Pakistan to the Arabian Sea for the Indus; Tibet to Assam to Bangladesh to the Bay of Bengal for the Brahmaputra; Uttarakhand to the Gangetic Plain to Bangladesh to the Bay of Bengal for the Ganges.

Common Mistakes, and How to Avoid Them

The Ganges is the longest because it is the most famous. Fame and length differ. The Ganges is the holiest river of Hinduism and supports hundreds of millions of people, but Britannica gives it as 2,510 kilometers, shorter than both the Indus and the Brahmaputra.

The Brahmaputra is the longest because it looks widest. Width and discharge do not equal length. Its Britannica length is about 2,900 kilometers, about 300 kilometers short of the Indus on the same set of figures.

The Indus is entirely in Pakistan. It is not. It rises in Tibet, flows through the Kashmir region, and only then flows through Pakistan, with tributaries draining parts of India and Afghanistan.

The Indus flows into the Bay of Bengal. It does not. It flows into the Arabian Sea through a delta south and southeast of Karachi. The Bay of Bengal is the mouth for the Ganges and Brahmaputra system.

Lengths from different websites can be compared directly. They often cannot, because sources may use different source points, mouth points, and methods. Compare rivers on one consistent set, or state the range.

Longest means largest or most important. It does not. Longest means greatest source to mouth length. A shorter river can carry more water or hold greater cultural significance, as the Ganges does.

The Indus length is exactly 3,200 kilometers. It is not exact. Britannica says “some 2,000 miles (3,200 km)”, which signals rounding. Quoting 3,200 kilometers without “about” overstates the precision.

Timeline

• About 1500 BCE: The Rigveda hymns mention the river named Sindhu, the source of the country name India, according to Britannica.
• 3rd millennium BCE: The Indus civilization develops in the Indus River valley, with Harappa and Mohenjo-daro among its large cities, according to Britannica.
• About 1850 onward: Modern irrigation engineering in the Indus valley leads to large canal systems, which by 1947 become the world’s greatest canal irrigation system, according to Britannica.
• 1947, 1958, and 2010: Major Indus floods recorded by Britannica, with embankments giving way and large areas flooded.
• 1960: The Indus Waters Treaty is signed between India and Pakistan, with the World Bank as a signatory, after nine years of negotiations, according to the World Bank.
• 2011: A Chinese research group announces an extended Indus figure of about 3,600 kilometers, based on satellite remeasurement and an alternative source point, reported in reference summaries without full published detail.
• 2026: Britannica’s main Indus article, as updated in 2026, gives the Indus length as some 2,000 miles, or 3,200 kilometers, the reference figure used for the ranking in this article.

Frequently Asked Questions

What is the longest river in South Asia? On the most commonly cited figures, the Indus River, at about 3,200 kilometers according to Encyclopaedia Britannica. Name the source, because other sources give different lengths, and the ranking depends on using one consistent set of figures.

How long is the Indus River? Britannica’s main article gives some 2,000 miles, or 3,200 kilometers. Other compilations give 2,880 kilometers or 3,180 kilometers, and a reported 2011 remeasurement gave about 3,600 kilometers without full published detail. The honest answer is a range with a named reference figure, not a single exact number.

Is the Brahmaputra longer than the Indus? Not on the Britannica set used here, where the Brahmaputra is about 2,900 kilometers, about 300 kilometers shorter. On some other pairings, with a short Indus figure and a long Brahmaputra figure, the gap closes or appears to reverse, which is why the source set must be stated.

Where does the Indus River start and end? It rises in southwestern Tibet, in China, near Lake Mapam, flows northwest through the Kashmir region, then south through Pakistan, and reaches the Arabian Sea through a delta south and southeast of Karachi.

What are the main tributaries of the Indus? In the mountains, the Zanskar, Shyok, Shigar, Gilgit, and Astor rivers, plus the Kabul River above Attock. On the Punjab Plain, the five rivers that give Punjab its name: the Jhelum, Chenab, Ravi, Beas, and Sutlej.

Is the Ganges the longest river in India? The Ganges, at 2,510 kilometers according to Britannica, is the longest river that rises in India and flows mainly through India and Bangladesh, but it is not the longest river in South Asia as a whole. The answer changes if the question is limited to rivers entirely inside India, so check the scope.

Why do different websites give different lengths for the same river? Because they choose different source points, mouth points, channels, and measurement methods, from small scale maps that smooth bends to satellite imagery that follows them. A length is a measurement with stated choices, not a fixed constant.

Does the Indus Waters Treaty give all Indus water to Pakistan? No. According to the World Bank, it allocates the western rivers, the Indus, Jhelum, and Chenab, to Pakistan, and the eastern rivers, the Ravi, Beas, and Sutlej, to India, while allowing each country certain uses on the other country’s rivers, with the Permanent Indus Commission and a limited procedural role for the World Bank.

Sources & references

• Encyclopaedia Britannica, Indus River article, opened 27 October 2026. Covers the Indus length as some 2,000 miles (3,200 km), drainage area, rise near Lake Mapam, course through Ladakh, Baltistan, Khyber Pakhtunkhwa, and the Punjab Plain, the Zanskar, Shyok, Shigar, Gilgit, Astor, Kabul, Jhelum, Chenab, Ravi, Beas, and Sutlej tributaries, Tarbela Dam, the Salt Range at Kalabagh, flood season and floods in 1947, 1958, and 2010, the delta near Thatta and south and southeast of Karachi, the Indus civilization and Rigveda name origin, irrigation history to 1947, and the Indus Waters Treaty of 1960.
• Encyclopaedia Britannica, Brahmaputra River summary, opened 27 October 2026. Covers the Brahmaputra as about 1,800 miles (2,900 km), its headsprings in the Tibet Autonomous Region as the Yarlung River, its passage through the Himalayas as the Dihang, its course through the Assam Valley and Bangladesh as the Jamuna, and its merger with the Ganges to form a vast delta, with irrigation and transportation importance.
• Encyclopaedia Britannica, Ganges River article, opened 27 October 2026. Covers the Ganges length as 1,560 miles (2,510 km), its five headstreams in Uttarakhand, the Alaknanda and Bhagirathi union at Devaprayag, its course through the Indo-Gangetic Plain, its Yamuna and Nepal tributaries, its passage into Bangladesh as the Padma, its union with the Brahmaputra and Meghna, the Ganges delta, the combined Ganges and Brahmaputra discharge, and its status as the holy river of Hinduism.
• Encyclopaedia Britannica Kids, Amu Darya article, consulted 27 October 2026. Covers the Amu Darya as 1,578 miles (2,540 km), from headwaters in the eastern Pamir Mountains in Afghanistan to its mouth on the southern shore of the Aral Sea in Uzbekistan.
• World Bank, Fact Sheet: The Indus Waters Treaty 1960 and the Role of the World Bank, opened 27 October 2026. Covers the treaty signing in 1960 after nine years of negotiations, the World Bank as signatory, allocation of western rivers to Pakistan and eastern rivers to India with certain uses allowed on the other country's rivers, the Permanent Indus Commission, question, difference, and dispute procedures, and the Bank's limited procedural role.