Ob

Ob
The Ob in Novosibirsk
Map of the Ob River watershed
Native nameОбь (Russian)
Location
CountryRussia
RegionAltai Krai, Novosibirsk Oblast, Tomsk Oblast, Khanty-Mansi Autonomous Okrug, Yamalia
CitiesBiysk, Barnaul, Novosibirsk, Nizhnevartovsk, Surgut
Physical characteristics
SourceKatun
  locationBelukha Mountain, Altai Republic
  coordinates49°45′0″N 86°34′0″E / 49.75000°N 86.56667°E / 49.75000; 86.56667
  elevation2,300 m (7,500 ft)
2nd sourceBiya
  locationLake Teletskoye, Altai Republic
  coordinates51°47′11″N 87°14′49″E / 51.78639°N 87.24694°E / 51.78639; 87.24694
  elevation434 m (1,424 ft)
3rd sourceMost distant source: Ob-Irtysh system
  locationnear Mang-tai-ch’ia-ta-fan pass, Altai Mountains, Xinjiang, China
  coordinates47°52′39″N 89°58′12″E / 47.87750°N 89.97000°E / 47.87750; 89.97000
  elevation2,960 m (9,710 ft)
Source confluenceNear Biysk
  locationAltai Krai
  coordinates52°25′54″N 85°01′26″E / 52.43167°N 85.02389°E / 52.43167; 85.02389
  elevation195 m (640 ft)
MouthGulf of Ob
  location
Ob Delta, Yamalia
  coordinates
66°32′02″N 71°23′41″E / 66.53389°N 71.39472°E / 66.53389; 71.39472
  elevation
0 m (0 ft)
Length3,700 km (2,300 mi)
Basin size2,972,497 km2 (1,147,688 sq mi) to 2,994,238 km2 (1,156,082 sq mi)
Width 
  minimum140 m (460 ft)
  average3,000 m (9,800 ft)
  maximum19,000 m (62,000 ft)
Depth 
  average9 m (30 ft)
  maximum40 m (130 ft)
Discharge 
  locationSalekhard (Basin size: 2,917,508 km2 (1,126,456 sq mi))
  average12,889 m3/s (455,200 cu ft/s)
(Period of data: 1971–2015)

12,475.1 m3/s (440,550 cu ft/s)
(Period of data: 1930–1984)

13,500 m3/s (480,000 cu ft/s)
(Period of data: 1999–2008)
  minimum2,360 m3/s (83,000 cu ft/s)
  maximum40,200 m3/s (1,420,000 cu ft/s)
Discharge 
  locationOb Estuary, Gulf of Ob (Kara Sea), Russia
  average402 km3/a (12,700 m3/s)
(Period of data: 1940–2017) 414 km3/a (13,100 m3/s)
(Period of data: 1984–2018)
Basin features
Tributaries 
  leftKatun, Anuy, Charysh, Aley, Parabel, Vasyugan, Irtysh, Severnaya Sosva
  rightBiya, Berd, Inya, Tom, Chulym, Ket, Tym, Vakh, Pim, Kazym

The Ob (/ˈɒb/; Russian: Обь) is a major river in Russia. It is in western Siberia, and with its tributary the Irtysh forms the world's seventh-longest river system, at 5,410 kilometres (3,360 mi). The Ob forms at the confluence of the Biya and Katun which have their origins in the Altai Mountains. It is the westernmost of the three great Siberian rivers that flow into the Arctic Ocean (the other two being the Yenisei and the Lena). Its flow is north-westward, then northward.

The main city on its banks is Novosibirsk, the largest city in Siberia, and the third-largest city in Russia. It is where the Trans-Siberian Railway crosses the river.

The Gulf of Ob is the world's longest estuary.