This is a list of the longest rivers on Earth. It includes river systems over 1,000 kilometers.
Contents |
The length of a river can be very hard to calculate. There are many factors, such as the source, the identification or the definition of the mouth, and the scale of measurement[1] of the river length between source and mouth, that determine the precise meaning of "river length". As a result, the length measurements of many rivers are only approximations. In particular, there has long been disagreement as to whether the Nile or the Amazon is the world's longest river. The Nile has traditionally been considered longer, but in recent years some Brazilian and Peruvian studies have suggested that the Amazon is longer by measuring the river plus the adjacent Pará estuary and the longest connecting tidal canal.[2][3][4][5]
For the purpose of determining maximum length a river's "true source" is considered to be the source of whichever tributary is farthest from the mouth. This tributary may or may not have the same name as the main stem river. For example, the source of the Mississippi River is normally said to be Lake Itasca in the U.S. state of Minnesota, but the most distant source in the Mississippi system is that of the Jefferson River in the state of Montana, a tributary of the Missouri River which in turn is a tributary of the Mississippi. When the Mississippi is measured from mouth to this farthest source, it is called the Mississippi-Missouri-Jefferson. Furthermore, it is sometimes hard to state exactly where a river begins, especially rivers that are formed by ephemeral streams, swamps, or changing lakes. In this article, length means the length of the longest continuous river channel in a given river system, regardless of name.
The mouth of a river is hard to determine in cases where the river has a large estuary that gradually widens and opens into the ocean; examples are the River Plate and the Saint Lawrence River. Some rivers, like the Okavango, Humboldt, and Kern do not have a mouth; instead they dwindle to very low water volume and eventually evaporate, or sink into an aquifer, or get diverted for agriculture. The exact point where these rivers end will vary seasonally.
The source of some rivers starting in farming areas can be difficult to determine, if the river is formed by the confluence of several farm field drainage ditches which only contain water after rain. Similarly, in rivers starting in a chalk area, such as the Chilterns in south England, the length of the upper course which is dry varies with how high the water table is, which varies with the weather: see winterbourne (stream).
The length of a river between source and mouth may be hard to determine due to issues of map scale. Small scale maps (those showing large areas) tend to generalize, or "smooth" lines more than large scale maps (those showing small areas). According to the generally accepted ideal, length measurements should be based on maps that are of a large enough scale to show the width of the river, and the path measured is the path a small boat would take down the middle of the river.
Even when detailed maps are available, the length measurement is not always clear. A river may have multiple channels, or anabranches. The length may depend on whether the center or the edge of the river is measured. It may not be clear how to measure the length through a lake. Seasonal and annual changes may alter both rivers and lakes. Other factors that can change the length of a river include cycles of erosion and flooding, dams, levees, and channelization. In addition, the length of meanders can change significantly over time due to natural or artificial cutoffs, when a new channel cuts across a narrow strip of land, bypassing a large river bend. For example, due to 18 cutoffs created between 1766 and 1885 the length of the Mississippi River from Cairo, Illinois, to New Orleans, Louisiana, was reduced by 218 miles (351 km).[6]
These points make it difficult, if not impossible, to get an accurate measurement of the length of a river. The varying accuracy and precision also makes it difficult to make length comparisons between different rivers without a degree of uncertainty.
One should take the aforementioned discussion into account when using the data in the following table. For most rivers, different sources provide conflicting information on the length of a river system. The information in different sources is between parentheses.
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River | Length (km) | Length (miles) | Drainage area (km²) | Average discharge (m³/s) | Outflow | Countries in the drainage basin | |
---|---|---|---|---|---|---|---|
1. | Nile – Kagera[n 1] | 6,650 (6,853) |
4,132 (4,258) |
3,349,000 | 5,100 | Mediterranean Sea | Ethiopia, Eritrea, Sudan, Uganda, Tanzania, Kenya, Rwanda, Burundi, Egypt, Democratic Republic of the Congo, South Sudan |
2. | Amazon – Ucayali – Apurímac[n 1] | 6,400 (6,992) |
3,976 (4,345) |
6,915,000 | 219,000 | Atlantic Ocean | Brazil, Peru, Bolivia, Colombia, Ecuador, Venezuela, Guyana |
3. | Yangtze (Chang Jiang) |
6,300 |
3,917 |
1,800,000 | 31,900 | East China Sea | China |
4. | Mississippi – Missouri – Jefferson | 6,275 |
3,902 |
2,980,000 | 16,200 | Gulf of Mexico | United States (98.5%), Canada (1.5%) |
5. | Yenisei – Angara – Selenge | 5,539 |
3,445 |
2,580,000 | 19,600 | Kara Sea | Russia (97%), Mongolia (2.9%) |
6. | Yellow River (Huang He) |
5,464 |
3,395 |
745,000 | 2,110 | Bohai Sea | China |
7. | Ob – Irtysh | 5,410 | 3,364 | 2,990,000 | 12,800 | Gulf of Ob | Russia, Kazakhstan, China, Mongolia |
8. | Paraná - Río de la Plata | 4,880 |
3,030 |
2,582,672 | 18,000 | Río de la Plata | Brazil (46.7%), Argentina (27.7%), Paraguay (13.5%), Bolivia (8.3%), Uruguay (3.8%) |
9. | Congo – Chambeshi (Zaïre) |
4,700 |
2,922 |
3,680,000 | 41,800 | Atlantic Ocean | Democratic Republic of the Congo, Central African Republic, Angola, Republic of the Congo, Tanzania, Cameroon, Zambia, Burundi, Rwanda |
10. | Amur – Argun (Heilong Jiang) |
4,444 | 2,763 | 1,855,000 | 11,400 | Sea of Okhotsk | Russia, China, Mongolia |
11. | Lena | 4,400 |
2,736 |
2,490,000 | 17,100 | Laptev Sea | Russia |
12. | Mekong (Lancang Jiang) |
4,350 | 2,705 | 810,000 | 16,000 | South China Sea | Laos, Thailand, China, Cambodia, Vietnam, Myanmar |
13. | Mackenzie – Peace – Finlay | 4,241 |
2,637 |
1,790,000 | 10,300 | Beaufort Sea | Canada |
14. | Niger | 4,200 |
2,611 |
2,090,000 | 9,570 | Gulf of Guinea | Nigeria (26.6%), Mali (25.6%), Niger (23.6%), Algeria (7.6%), Guinea (4.5%), Cameroon (4.2%), Burkina Faso (3.9%), Côte d'Ivoire, Benin, Chad |
15. | Murray – Darling | 3,672[8] |
2,282 |
1,061,000 | 767 | Southern Ocean | Australia |
16. | Tocantins – Araguaia | 3,650 | 2,270 | 950,000 | 13,598 | Atlantic Ocean, Amazon | Brazil |
17. | Volga | 3,645 | 2,266 | 1,380,000 | 8,080 | Caspian Sea | Russia |
18. | Shatt al-Arab – Euphrates | 3,596 |
2,236 |
884,000 | 856 | Persian Gulf | Iraq (60.5%), Turkey (24.8%), Syria (14.7%) |
19. | Madeira – Mamoré – Grande – Caine – Rocha | 3,380 | 2,100 | 1,485,200 | 31,200 | Amazon | Brazil, Bolivia, Peru |
20. | Purus | 3,211 | 1,995 | 63,166 | 8,400 | Amazon | Brazil, Peru |
21. | Yukon | 3,185 | 1,980 | 850,000 | 6,210 | Bering Sea | United States (59.8%), Canada (40.2%) |
22. | Indus | 3,180 | 1,976 | 960,000 | 7,160 | Arabian Sea | Pakistan (93%), India, China |
23. | São Francisco | 3,180* (2,900) |
1,976* (1,802) |
610,000 | 3,300 | Atlantic Ocean | Brazil |
24. | Syr Darya – Naryn | 3,078 | 1,913 | 219,000 | 703 | Aral Sea | Kazakhstan, Kyrgyzstan, Uzbekistan, Tajikistan |
25. | Salween (Nu Jiang) |
3,060 | 1,901 | 324,000 | 3,153[9] | Andaman Sea | China (52.4%), Myanmar (43.9%), Thailand (3.7%) |
26. | Saint Lawrence – Niagara – Detroit – Saint Clair – Saint Marys – Saint Louis | 3,058 | 1,900 | 1,030,000 | 10,100 | Gulf of Saint Lawrence | Canada (52.1%), United States (47.9%) |
27. | Rio Grande | 3,057 (2,896) |
1,900 (1,799) |
570,000 | 82 | Gulf of Mexico | United States (52.1%), Mexico (47.9%) |
28. | Lower Tunguska | 2,989 | 1,857 | 473,000 | 3,600 | Yenisei | Russia |
29. | Brahmaputra – Tsangpo | 2,948* | 1,832* | 1,730,000 | 19,200[10] | Bay of Bengal | India (58.0%), China (19.7%), Nepal (9.0%), Bangladesh (6.6%), Disputed India/China (4.2%), Bhutan (2.4%) |
30. | Danube – Breg
(Duna) |
2,888* | 1,795* | 817,000 | 7,130 | Black Sea | Romania (28.9%), Hungary (11.7%), Austria (10.3%), Serbia (10.3%), Germany (7.5%), Slovakia (5.8%), Bulgaria (5.2%), Croatia (4.5%), |
31. | Zambezi (Zambesi) |
2,693* | 1,673* | 1,330,000 | 4,880 | Mozambique Channel | Zambia (41.6%), Angola (18.4%), Zimbabwe (15.6%), Mozambique (11.8%), Malawi (8.0%), Tanzania (2.0%), Namibia, Botswana |
32. | Vilyuy | 2,650 | 1,647 | 454,000 | 1,480 | Lena | Russia |
33. | Araguaia | 2,627 | 1,632 | 358,125 | 5,510 | Tocantins | Brazil |
34. | Ganges – Hooghly - Padma
(Ganga) |
2,620[11] | 1,630 | 907,000 | 12,037[12] | Bay of Bengal | India, Bangladesh |
34. | Amu Darya -- Panj | 2,620 | 1,628 | 534,739 | 1,400 | Aral Sea | Uzbekistan, Turkmenistan, Tajikistan, Afghanistan |
35. | Japurá (Rio Yapurá) |
2,615* | 1,625* | 242,259 | 6,000 | Amazon | Brazil, Colombia |
36. | Nelson – Saskatchewan | 2,570 | 1,597 | 1,093,000 | 2,575 | Hudson Bay | Canada, United States |
37. | Paraguay (Rio Paraguay) |
2,549 | 1,584 | 900,000 | 4,300 | Paraná | Brazil, Paraguay, Bolivia, Argentina |
38. | Kolyma | 2,513 | 1,562 | 644,000 | 3,800 | East Siberian Sea | Russia |
40. | Pilcomayo | 2,500 | 1,553 | 270,000 | Paraguay | Paraguay, Argentina, Bolivia | |
41. | Upper Ob -- Katun | 2,490 | 1,547 | Ob | Russia | ||
42. | Ishim | 2,450 | 1,522 | 177,000 | 56 | Irtysh | Kazakhstan, Russia |
43. | Juruá | 2,410 | 1,498 | 200,000 | 6,000 | Amazon | Peru, Brazil |
44. | Ural | 2,428 | 1,509 | 237,000 | 475 | Caspian Sea | Russia, Kazakhstan |
45. | Arkansas | 2,348 | 1,459 | 505,000 (435,122) |
1,066 | Mississippi | United States |
47. | Olenyok | 2,292 | 1,424 | 219,000 | 1,210 | Laptev Sea | Russia |
48. | Dnieper | 2,287 | 1,421 | 516,300 | 1,670 | Black Sea | Russia, Belarus, Ukraine |
49. | Aldan | 2,273 | 1,412 | 729,000 | 5,060 | Lena | Russia |
46. | Ubangi – Uele[13] | 2,270 | 1,410 | 772,800 | 4,000 | Congo | Democratic Republic of the Congo, Central African Republic, Republic of Congo |
50. | Negro | 2,250 | 1,450 | 720,114 | 26,700 | Amazon | Brazil, Venezuela, Colombia |
51. | Columbia | 2,250 (1,953) | 1,450 (1,214) | 415,211 | 7,500 | Pacific Ocean | United States, Canada |
52. | Colorado (western U.S.) | 2,333 | 1,450 | 390,000 | 1,200 | Gulf of California | United States, Mexico |
53. | Pearl – Zhu Jiang | 2,200 | 1,376 | 437,000 | 13,600 | South China Sea | China (98.5%), Vietnam (1.5%) |
54. | Red (USA) | 2,188 | 1,360 | 78,592 | 875 | Mississippi | United States |
55. | Ayeyarwady (Irrawaddy) |
2,170 | 1,348 | 411,000 | 13,000 | Andaman Sea | Myanmar |
56. | Kasai | 2,153 | 1,338 | 880,200 | 10,000 | Congo | Angola, Democratic Republic of the Congo |
57. | Ohio – Allegheny | 2,102 | 1,306 | 490,603 | 7,957 | Mississippi | United States |
58. | Orinoco | 2,101 | 1,306 | 1,380,000 | 33,000 | Atlantic Ocean | Venezuela, Colombia, Guyana |
59. | Tarim | 2,100 | 1,305 | 557,000 | Lop Nur | P. R. China | |
60. | Xingu | 2,100 | 1,305 | Amazon | Brazil | ||
61. | Orange | 2,092 | 1,300 | Atlantic Ocean | South Africa, Namibia, Botswana, Lesotho | ||
62. | Northern Salado | 2,010 | 1,249 | Paraná | Argentina | ||
63. | Vitim | 1,978 | 1,229 | Lena | Russia | ||
64. | Tigris | 1,950 | 1,212 | Shatt al-Arab | Turkey, Iraq, Syria | ||
65. | Songhua | 1,927 | 1,197 | Amur | P. R. China | ||
66. | Tapajós | 1,900 | 1,181 | Amazon | Brazil | ||
67. | Don | 1,870 | 1,162 | 425,600 | 935 | Sea of Azov | Russia, Ukraine |
68. | Stony Tunguska | 1,865 | 1,159 | 240,000 | Yenisei | Russia | |
69. | Pechora | 1,809 | 1,124 | 322,000 | Barents Sea | Russia | |
70. | Kama | 1,805 | 1,122 | 507,000 | Volga | Russia | |
71. | Limpopo | 1,800 | 1,118 | 413,000 | Indian Ocean | Mozambique, Zimbabwe, South Africa, Botswana | |
72. | Guaporé (Itenez) | 1,749 | 1,087 | Mamoré | Brazil, Bolivia | ||
73. | Indigirka | 1,726 | 1,072 | 360,400 | 1,810 | East Siberian Sea | Russia |
74. | Snake | 1,670 | 1,038 | 279,719 | 1,611 | Columbia | United States |
75. | Senegal | 1,641 | 1,020 | 419,659 | Atlantic Ocean | Senegal, Mali, Mauritania | |
76. | Uruguay | 1,610 | 1,000 | 370,000 | Atlantic Ocean | Uruguay, Argentina, Brazil | |
77. | Murrumbidgee River | 1,600 | 994 | [[]] | Australia | ||
77. | Blue Nile | 1,600 | 994 | 326,400 | Nile | Ethiopia, Sudan | |
77. | Churchill | 1,600 | 994 | Hudson Bay | Canada | ||
77. | Khatanga | 1,600 | 994 | Laptev Sea | Russia | ||
77. | Okavango | 1,600 | 994 | Okavango Delta | Namibia, Angola, Botswana | ||
77. | Volta | 1,600 | 994 | Gulf of Guinea | Ghana, Burkina Faso, Togo, Côte d'Ivoire, Benin | ||
82. | Beni | 1,599 | 994 | 283,350 | 8,900 | Madeira | Bolivia |
83. | Platte | 1,594 | 990 | Missouri | United States | ||
84. | Tobol | 1,591 | 989 | Irtysh | Kazakhstan, Russia | ||
85. | Jubba – Shebelle | 1,580* | 982* | Indian Ocean | Ethiopia, Somalia | ||
86. | Içá (Putumayo) | 1,575 | 979 | Amazon | Brazil, Peru, Colombia, Ecuador | ||
87. | Magdalena | 1,550 | 963 | 263,858 | 9,000 | Caribbean Sea | Colombia |
88. | Han | 1,532 | 952 | Yangtze | P. R. China | ||
89. | Oka | 1,500 | 932 | Volga | Russia | ||
91. | Pecos | 1,490 | 926 | Rio Grande | United States | ||
92. | Upper Yenisei -- Little Yenisei (Kaa-Hem) | 1,480 | 920 | Yenisei | Russia, Mongolia | ||
93. | Godavari | 1,465 | 910 | Bay of Bengal | India | ||
94. | Colorado (Texas) | 1,438 | 894 | Gulf of Mexico | United States | ||
95. | Río Grande (Guapay) | 1,438 | 894 | 102,600 | 264 | Ichilo | Bolivia |
96. | Belaya | 1,420 | 882 | Kama | Russia | ||
97. | Cooper – Barcoo | 1,420 | 880 | Lake Eyre | Australia | ||
98. | Marañón | 1,415 | 879 | Amazon | Peru | ||
99. | Dniester | 1,411 (1,352) | 877 (840) | Black Sea | Ukraine, Moldova | ||
100. | Benue | 1,400 | 870 | Niger | Cameroon, Nigeria | ||
100. | Ili (Yili) |
1,400 | 870 | Lake Balkhash | P. R. China, Kazakhstan | ||
100. | Warburton – Georgina | 1,400 | 870 | Lake Eyre | Australia | ||
103. | Sutlej | 1,372 | 852 | Chenab | China, India, Pakistan | ||
104. | Yamuna | 1,370 | 851 | Ganges | India | ||
105. | Vyatka | 1,370 | 851 | Kama | Russia | ||
106. | Fraser | 1,368 | 850 | 220,000 | 3,475 | Pacific Ocean | Canada |
107. | Mtkvari (Kura) | 1,364 | 848 | Caspian Sea | Azerbaijan, Georgia, Armenia, Turkey, Iran | ||
108. | Grande | 1,360 | 845 | Paraná | Brazil | ||
109. | Brazos | 1,352 | 840 | Gulf of Mexico | United States | ||
110. | Cauca | 1,350 | 839 | Magdalena | Colombia | ||
111. | Liao | 1,345 | 836 | Bo Hai | P. R. China | ||
112. | Yalong | 1,323 | 822 | Yangtze | P. R. China | ||
113. | Iguaçu | 1,320 | 820 | Paraná | Brazil, Argentina | ||
113. | Olyokma | 1,320 | 820 | Lena | Russia | ||
115. | Northern Dvina – Sukhona | 1,302 | 809 | 357,052 | 3,332 | White Sea | Russia |
116. | Krishna | 1,300 | 808 | Bay of Bengal | India | ||
116. | Iriri | 1,300 | 808 | Xingu | Brazil | ||
117. | Narmada | 1,289 | 801 | Arabian Sea | India | ||
118. | Lomami[14] | 1,280 | 795 | Congo | Democratic Republic of the Congo | ||
119. | Ottawa | 1,271 | 790 | Saint Lawrence | Canada | ||
120. | Zeya | 1,242 | 772 | Amur | Russia | ||
121. | Juruena | 1,240 | 771 | Tapajós | Brazil | ||
122. | Upper Mississippi | 1,236 | 768 | Mississippi | United States | ||
123. | Rhine | 1,233 | 768 | 198,735 | 2,330 | North Sea | Germany, France, Switzerland, Netherlands, Austria, Liechtenstein, Italy (minimal), Belgium, Luxembourg |
124. | Athabasca | 1,231 | 765 | 95,300 | Mackenzie | Canada | |
124. | Elbe – Vltava | 1,252 | 778 | 148,268 | 711 | North Sea | Germany, Czech Republic |
126. | Canadian | 1,223 | 760 | Arkansas | United States | ||
127. | North Saskatchewan | 1,220 | 758 | Saskatchewan | Canada | ||
128. | Draa | 1,218 | 994 | Atlantic Ocean | Morocco | ||
129. | Vaal | 1,210 | 752 | Orange | South Africa | ||
130. | Shire | 1,200 | 746 | Zambezi | Mozambique, Malawi | ||
131. | Nen (Nonni) |
1,190 | 739 | Songhua | P. R. China | ||
132. | Kızıl River | 1,182 | 734 | 115,000 | 400 | Black Sea | Turkey |
133. | Green | 1,175 | 730 | Colorado (western U.S.) | United States | ||
134. | Milk | 1,173 | 729 | Missouri | United States, Canada | ||
135. | Chindwin | 1,158 | 720 | Ayeyarwady | Myanmar | ||
136. | Sankuru | 1,150 | 715 | Kasai | Democratic Republic of the Congo | ||
137. | Red (Asia) | 1,149 | 714 | 143,700 | 2,640 | Gulf of Tonkin | China, Vietnam |
138. | James (Dakotas) | 1,143 | 710 | Missouri | United States | ||
139. | Kapuas | 1,143 | 710 | South China Sea | Indonesia | ||
140. | Desna | 1,130 | 702 | 88,900 | 360 | Dnieper | Russia, Belarus, Ukraine |
140. | Helmand | 1,130 | 702 | Hamun-i-Helmand | Afghanistan, Iran | ||
140. | Madre de Dios | 1,130 | 702 | 125,000 | 4,915 | Beni | Peru, Bolivia |
140. | Tietê | 1,130 | 702 | Paraná | Brazil | ||
140. | Vychegda | 1,130 | 702 | Northern Dvina | Russia | ||
145. | Sepik | 1,126 | 700 | 77,700 | Pacific Ocean | Papua New Guinea, Indonesia | |
146. | Cimarron | 1,123 | 698 | Arkansas | United States | ||
147. | Anadyr | 1,120 | 696 | Gulf of Anadyr | Russia | ||
147. | Paraíba do Sul | 1,120 | 696 | Atlantic Ocean | Brazil | ||
149. | Jialing River | 1,119 | 695 | Yangtze | P. R. China | ||
150. | Liard | 1,115 | 693 | Mackenzie | Canada | ||
151. | Cumberland | 1,105 | 687 | 46,830 | 862 | Mississippi | United States |
152. | White | 1,102 | 685 | Mississippi | United States | ||
153. | Huallaga | 1,100 | 684 | Marañón | Peru | ||
153. | Kwango | 1,100 | 684 | 263,500 | 2,700 | Kasai | Angola, Democratic Republic of the Congo |
155. | Gambia | 1,094 | 680 | Atlantic Ocean | The Gambia, Senegal, Guinea | ||
156. | Chenab | 1,086 | 675 | Indus | India, Pakistan | ||
157. | Yellowstone | 1,080 | 671 | 114,260 | Missouri | United States | |
158. | Aras | 1,072 | 665 | 102,000 | 285 | Kura | Turkey, Armenia, Azerbaijan, Iran |
159. | Chu River | 1,067 | 663 | 62,500 | none | Kyrgyzstan, Kazakhstan | |
160. | Seversky Donets | 1,078 (1,053) | 670 (654) | Don | Russia, Ukraine | ||
161. | Bermejo | 1,050 | 652 | Paraguay | Argentina, Bolivia | ||
161. | Fly | 1,050 | 652 | Gulf of Papua | Papua New Guinea, Indonesia | ||
161. | Guaviare | 1,050 | 652 | Orinoco | Colombia | ||
161. | Kuskokwim | 1,050 | 652 | Bering Sea | United States | ||
165. | Tennessee | 1,049 | 652 | Ohio | United States | ||
166. | Vistula | 1,047 | 630 | 194,424 | 1,080 | Baltic Sea | Poland |
167. | Aruwimi[14] | 1,030 | 640 | Congo River | Democratic Republic of the Congo | ||
168. | Daugava | 1,020 | 634 | 87,900 | 678 | Gulf of Riga | Latvia, Belarus, Russia |
169. | Gila | 1,015 | 631 | Colorado (western U.S.) | United States | ||
170. | Loire | 1,012 | 629 | 115,271 | 840 | Atlantic Ocean | France |
171. | Essequibo | 1,010 | 628 | Atlantic Ocean | Guyana | ||
171. | Khoper | 1,010 | 628 | Don | Russia | ||
173. | Tagus (Tajo/Tejo) |
1,006 | 625 | 80,100 | Atlantic Ocean | Spain, Portugal |
The Amazon basin formerly drained westwards into the Pacific Ocean, until the Andes rose and reversed the drainage.[16]
The Congo basin is completely surrounded by high land, except for its long narrow exit valley past Kinshasa, including waterfalls around Manyanga. That gives the impression that most of the Congo basin was formerly on a much higher land level and that it was rejuvenated by much of its lower course being removed.
Prior to the tectonic breakup of Pangea during Permian and early Triassic times, Africa and South America were part of one super continent, and the Congo probably drained into the Amazon basin and eventually into the Pacific. Including part of its course that was completely lost when the South Atlantic opened, its total course may have been anything up to approximately 12,000 km (7,500 mi) long.
This river would have been about 10,000 km (6,200 mi) long, in the last Ice Age. See West Siberian Glacial Lake. Its longest headwater was the Selenga river of Mongolia: it drained through ice-dammed lakes and the Aral Sea and the Caspian Sea to the Black Sea.
Formerly Lake Tanganyika drained northwards into the Albert Nile, making the Nile somewhere around 700 miles longer, until in the Miocene the Virunga Volcanoes arose and blocked its course. Also, when the Mediterranean Sea was dry during the Messinian Salinity Crisis, the Nile extended northwards over the dry seabed and thus may have gained 100 miles or more in length.
The Eridanos was a large river during the Baventian Stage about two million years ago in the late early Pleistocene, when the Baltic Sea was all land. It was about 2700 kilometres or about 1700 miles long, a little shorter than the modern Danube. It began in Lapland, and then flowed through the area of the modern-day Gulf of Bothnia and Baltic Sea to western Europe, where it had an immense delta which spanned almost all the current North Sea. It was comparable in size to the current-day Amazon River mouth.
Similarly to the Nile, during the Messinian Salinity Crisis, the Po would have extended its course south-eastwards in what is today the seabed of the Adriatic Sea, more or less doubling its current length (652 km), likely varying seasonally according to how far it managed to flow across the hot dry seabed until it dried.