The Orinoco (Spanish pronunciation: [oɾiˈnoko]) is one of the longest rivers in South America at 2,140 km (1,330 mi).

Its drainage basin, sometimes known as the Orinoquia, covers ca 1 million km, with 65% of it in Venezuela and the 35% in Colombia. It is the fourth largest river in the world by discharge volume of water. The nevertheless high volume flow (39,000 m/s at delta) of the Orinoco can be explained by the high precipitation in almost the entire catchment area (ca 2,300 mm/a). The Orinoco River and its tributaries are the major transportation system for eastern and interior Venezuela and the Llanos of Colombia. The environment and wildlife in the Orinoco's basin are extremely diverse.

The river's name is derived from the Warao term for "a place to paddle", itself derived from the terms güiri (paddle) and noko (place) i.e. a navigable place.

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. Find sources: "Orinoco" – news · newspapers · books · scholar · JSTOR (December 2022) (Learn how and when to remove this message)

The mouth of the Orinoco River at the Atlantic Ocean was documented by Christopher Columbus on 1 August 1498, during his third voyage. Its source at the Cerro Delgado–Chalbaud, in the Parima range, was not explored until 453 years later, in 1951. The source, near the Venezuelan–Brazilian border, at 1,047 metres (3,435 ft) above sea level (2°19′05″N 63°21′42″W / 2.31806°N 63.36167°W / 2.31806; -63.36167), was explored in 1951 by a joint French-Venezuelan expedition.

The Orinoco, as well as its tributaries in the eastern llanos such as the Apure and Meta, were explored in the 16th century by German expeditions under Ambrosius Ehinger and his successors. In 1531, starting at the principal outlet in the delta, the Boca de Navios, Diego de Ordaz sailed up the river to the Meta. Antonio de Berrio sailed down the Casanare to the Meta, and then down the Orinoco River and back to Coro. In 1595, after capturing de Berrio to obtain information while conducting an expedition to find the fabled city of El Dorado, the Englishman Sir Walter Raleigh sailed down the river, reaching the savanna country.

From April to May 1800, the Prussian-born Alexander von Humboldt and his companion, Aime Bonpland, explored stretches of the Orinoco, supported by indigenous helpers and guided by his interest to prove that South America's waterways formed an interconnected system from the Andes to the Amazon. He reported on the pink river dolphins and later published extensively on the river's flora and fauna.

The sources of the Orinoco River, located at Cerro Carlos Delgado Chalbaud (2º19’05” N, 63º21’42” W), were discovered in 1951 by the French-Venezuelan expedition that went back and explored the Upper Orinoco course to the Sierra Parima near the border with Brazil, headed by Venezuelan army officer Frank Risquez Iribarren.

The first bridge across the Orinoco River, the Angostura Bridge at Ciudad Bolívar, Venezuela, was completed in 1967.

In 1968, an expedition was set off by National Geographic and Hovercraft from Manaus (Brazil) to Port of Spain (Trinidad). Aboard a SR.N6 hovercraft, the expedition members followed the Negro river upstream to where it is joined by the Casiquiare canal, on the border between Colombia and Venezuela. After following the Casiquiare to the Orinoco River they hovered thru perilous rapids of the rivers Maipures and Atures. The Orinoco was then traversed down to its mouths in the Gulf of Paria and then to Port of Spain. The primary purpose of the expedition was filming for the BBC series The World About Us episode "The Last Great Journey on Earth from Amazon to Orinoco by Hovercraft", which aired in 1970, and demonstrated the abilities of a hovercraft, thereby promoting sales of this British invention.

The first powerline crossing of the Orinoco River was completed in 1981 for an 800 kV TL single span of 1,200 metres (3,900 ft) using two towers 110 metres (360 ft) tall.

In 1992, an overhead power line crossing for two 400 kV-circuits was completed just west of Morocure (between the cities of Ciudad Bolívar and Ciudad Guayana), north of the confluence of Routes 1 and 19. It had three towers, and the two spans measured 2,161 metres (7,090 ft) and 2,537 metres (8,323 ft), respectively.

In 2006, a second bridge, known as the Orinoquia Bridge, was completed near Ciudad Guayana, Venezuela.

The course of the Orinoco forms a wide ellipsoidal arc, surrounding the Guiana Shield; it is divided in four stretches of unequal length that very roughly correspond to the longitudinal zonation of a typical large river:

• Upper Orinoco – 286 kilometres (178 mi) long, from its headwaters to the Raudales de Guaharibos rapids, flows through mountainous landscape in a northwesterly direction
• Middle Orinoco – 805 kilometres (500 mi) long, divided into two sectors, the first of which ca. 515 kilometres (320 mi) long has a general westward direction down to the confluence with the Atabapo and Guaviare rivers at San Fernando de Atabapo; the second flows northward, for about 290 kilometres (180 mi), along the Venezuelan–Colombian border, flanked on both sides by the westernmost granitic upwellings of the Guiana Shield which impede the development of a flood plain, to the Atures rapids near the confluence with the Meta River at Puerto Carreño
• Lower Orinoco – 959 kilometres (596 mi) long with a well-developed alluvial plain, flows in a northeast direction, from Atures rapids down to Piacoa in front of Barrancas
• Delta Amacuro – 200 kilometres (120 mi) long that empties into the Gulf of Paría and the Atlantic Ocean, a very large delta, some 22,500 km (8,700 sq mi) and 370 kilometres (230 mi) at its widest.

At its mouth, the Orinoco River forms a wide delta that branches off into hundreds of rivers and waterways that flow through 41,000 km (16,000 sq mi) of swampy forests. In the rainy season, the Orinoco River can swell to a breadth of 22 kilometres (14 mi) and a depth of 100 metres (330 ft).

Most of the important Venezuelan rivers are tributaries of the Orinoco River, the largest being the Caroní, which joins it at Puerto Ordaz, close to the Llovizna Falls. A peculiarity of the Orinoco river system is the Casiquiare canal, which starts as an arm of the Orinoco, and finds its way to the Rio Negro, a tributary of the Amazon, thus forming a 'natural canal' between Orinoco and Amazon.

The stream gradient of the entire river is 0.05% (1,047 m over 2,250 km). Downstream of Raudales de Guaharibos the gradient is 0.01% (183/1,964), which is also the gradient from Ciudad Bolivar to the ocean (54/435).

• Apure: from Venezuela through the east into the Orinoco
• Arauca: from Colombia to Venezuela east into the Orinoco
• Atabapo: from the Guiana Highlands of Venezuela north into the Orinoco
• Caroní: from the Guiana Highlands of Venezuela north into the Orinoco
• Casiquiare canal: in SE Venezuela, a distributary from the Orinoco flowing west to the Negro River, a major affluent to the Amazon
• Caura: from eastern Venezuela (Guiana Highlands) north into the Orinoco
• Guaviare: from Colombia east into the Orinoco
• Inírida: from Colombia southeast into the Guaviare.
• Meta: from Colombia, border with Venezuela east into the Orinoco
• Ventuari: from eastern Venezuela (the Guiana Highlands) southwest into the Orinoco
• Vichada: from Colombia east into the Orinoco

Average, minimum and maximum discharge at Ciudad Bolívar and Ciudad Guayana (Lower Orinoco):

Year	Discharge (m/s)
	Ciudad Bolívar			Ciudad Guayana
	Min	Mean	Max	Min	Mean	Max
2000	4,799	33,415	67,667			71,080
2001	3,438	25,695	59,527			60,493
2002	3,868	34,002	74,367			66,561
2003	3,287	34,728	74,367			77,802
2004	4,071	35,717	74,208			66,367
2005	5,439	31,980	64,800			57,471
2006	6,521	35,901	77,422			71,446
2007	3,949	34,477	71,527			65,611
2008	4,754	32,378	70,536
2009	7,419	26,041	59,671			67,992
2010	3,067	35,286	75,807		40,101	86,581
2011	6,368	37,957	74,367		40,189	92,258
2012	7,805	38,685	77,909		44,049	74,566
2013	5,581	32,041	65,850		36,484	62,151
2014	4,364	31,632	71,214		36,018	66,050
2015	5,725	29,476	71,136		33,742	65,903
2016	3,514	35,474	78,398		39,841	83,098
2017	7,520	34,302	77,315	8,936	39,057	85,997
2018	4,693	36,467	82,611	6,637	40,870	87,303
2019	4,846	32,017	72,203		34,620	70,248
2020	4,570	28,915	63,638	6,018	31,551	54,640
2021	7,279	39,378	74,873	9,199	42,786	79,487
2022	6,463	39,094	75,912	9,679	42,663	85,238
2023	8,377	32,523	68,742	8,774	36,380	81,831

Monthly average discharge (m/s) at Ciudad Bolívar (2018 to 2023):

Month	2018	2019	2020	2021	2022	2023	1926–2023
JAN	11,009	8,955	13,667	19,108	11,067	14,528	11,637
FEB	7,593	6,414	7,142	9,554	6,463	9,412	6,840
MAR	4,693	4,846	4,570	7,279	10,187	8,377	5,521
APR	6,862	5,634	5,080	16,378	13,860	10,036	7,347
MAY	27,262	17,343	11,688	33,363	28,156	19,290	20,295
JUN	46,541	36,447	29,204	63,086	50,344	41,963	39,205
JUL	73,295	57,240	42,542	68,208	68,499	59,398	57,550
AUG	82,611	72,203	57,742	74,873	75,912	68,742	69,207
SEP	70,591	69,859	63,638	68,441	73,589	67,129	66,502
OCT	50,838	48,298	50,060	53,294	54,020	52,622	51,206
NOV	34,852	34,644	36,926	36,518	45,509	23,332	35,752
DEC	21,457	22,317	24,718	22,437	31,527	15,450	22,974
Mean	36,467	32,017	28,915	39,378	39,094	32,523	32,836

Monthly average discharge (m/s) at Ciudad Guayana (1996 to 1998):

Month	1996	1997	1998	1943–1998
JAN	17,627	24,386	10,919	16,661
FEB	14,486	17,144	7,583	10,108
MAR	15,334	15,767	8,906	7,702
APR	12,514	12,615	12,411	10,609
MAY	23,670	25,152	32,751	26,317
JUN	45,781	43,142	49,062	45,179
JUL	61,177	55,597	63,659	58,412
AUG	67,639	61,275	67,756	64,975
SEP	65,933	53,825	66,416	63,244
OCT	57,912	38,742	54,189	53,201
NOV	45,267	28,372	38,345	40,805
DEC	36,094	21,116	30,130	29,229
Mean	38,620	33,094	36,844	35,537

Average discharge at Ciudad Bolívar (complete time series from 1926 to 2023):

Year	m/s	Year	m/s	Year	m/s
1926	23,376	1959	30,333	1992	28,571
1927	37,476	1960	31,818	1993	35,204
1928	32,838	1961	27,830	1994	35,110
1929	32,653	1962	32,930	1995	29,360
1930	30,610	1963	32,560	1996	35,992
1931	33,766	1964	27,736	1997	28,757
1932	33,302	1965	27,643	1998	35,000
1933	32,792	1966	29,220	1999	34,925
1934	34,137	1967	34,323	2000	33,415
1935	31,168	1968	32,280	2001	25,695
1936	31,260	1969	32,606	2002	34,002
1937	29,962	1970	34,600	2003	34,728
1938	37,383	1971	33,673	2004	35,717
1939	28,292	1972	36,177	2005	31,980
1940	25,232	1973	27,597	2006	35,901
1941	28,200	1974	26,344	2007	34,477
1942	31,540	1975	29,313	2008	32,378
1943	38,403	1976	37,290	2009	26,041
1944	34,878	1977	30,705	2010	35,286
1945	33,395	1978	32,514	2011	37,957
1946	36,363	1979	32,885	2012	38,685
1947	30,426	1980	35,018	2013	32,041
1948	31,818	1981	38,080	2014	31,632
1949	32,745	1982	36,224	2015	29,476
1950	32,096	1983	36,130	2016	35,474
1951	38,220	1984	31,493	2017	34,302
1952	33,858	1985	30,380	2018	36,467
1953	36,177	1986	35,040	2019	32,017
1954	38,310	1987	34,090	2020	28,915
1955	31,076	1988	30,472	2021	39,378
1956	36,734	1989	29,638	2022	39,094
1957	29,128	1990	33,442	2023	32,523
1958	28,108	1991	31,770	2024

The boto and the giant otter inhabit the Orinoco River system. The Orinoco crocodile is one of the rarest reptiles in the world. Its range in the wild is restricted to the middle and lower Orinoco River Basin.

More than 1000 fish species have been recorded in the river basin and about 15% are endemic. Among the fish in the river are species found in brackish or salt water in the Orinoco estuary, but also many restricted to fresh water. By far the largest orders are Characiformes and Siluriformes, which together account for more than 80% of the fresh water species. Some of the more famous are the black spot piranha and the cardinal tetra. The latter species, which is important in the aquarium industry, is also found in the Rio Negro, revealing the connection between this river and the Orinoco through the Casiquiare canal. Because the Casiquiare includes both blackwater and clear- to whitewater sections, only relatively adaptable species are able to pass through it between the two river systems.

The river is navigable for most of its length, and dredging enables ocean ships to go as far as Ciudad Bolívar, at the confluence of the Caroní River, 435 kilometres (270 mi) upstream. River steamers carry cargo as far as Puerto Ayacucho and the Atures Rapids.

In 1926, a Venezuelan mining inspector found one of the richest iron ore deposits near the Orinoco delta, south of the city of San Felix on a mountain named El Florero. Full-scale mining of the ore deposits began after World War II, by a conglomerate of Venezuelan firms and US steel companies. At the start in the early 1950s, about 10,000 tons of ore-bearing soil was mined per day.

The Orinoco River deposits also contain extensive tar sands in the Orinoco oil belt, which may be a source of future oil production.

Encompassing the states of Anzoategui-Guarico and Monagas states, the Interior Range forms the northern boundary and the Guayana Shield the southern boundary. Maturin forms the eastern subbasin and Guarico forms the western subbasin. The El Furrial oil field was discovered in 1978, producing from late Oligocene shallow marine sandstones in an overthrusted foreland basin.

Since 1973, the Civil Association Nuestros Rios son Navegables organize the Internacional Rally Nuestros Rios son Navegables, a motonautical round trip of over 1,200 kilometers through the Orinoco, Meta and Apure Rivers. Starting out from Ciudad Bolívar or San Fernando de Apure, is the longest fluvial rally in the world with the participation of worldwide competitors, more than 30 support boats, logistics teams, thousands of tourists and fans travel. The boats had an average speed of 120 miles per hour.

Since 1988, the local government of Ciudad Guayana has conducted a swim race in the rivers Orinoco and Caroní, with up to 1,000 competitors. Since 1991, the Paso a Nado Internacional de los Rios Orinoco–Caroní has been celebrated every year, on a Sunday close to 19 April. Worldwide, this swim-meet has grown in importance, and it has a large number of competitors. The 26th meet was held in 2016.

The Irish singer and songwriter Enya wrote and sang the song "Orinoco Flow", which she released in 1988. Jules Verne's novel Superbe Orénoque has the river as its central theme.

• Adaheli, the Sun in the mythology of the Orinoco region
• Fishes of the Orinoco in the Wild (2020) book
• "Orinoco Flow" – the song uses the Orinoco and its environs as a theme for its lyrics

• Stark, James H. 1897. Stark's Guide-Book and History of Trinidad including Tobago, Granada, and St. Vincent; also a trip up the Orinoco and a description of the great Venezuelan Pitch Lake. Boston, James H. Stark, publisher; London, Sampson Low, Marston & Company. (This book has an excellent description of a trip up the Orinoco as far as Ciudad Bolívar and a detailed description of the Venezuelan Pitch Lake situated on the western side of the Gulf of Paria opposite.)
• MacKee, E.D., Nordin, C.F. and D. Perez-Hernandez (1998). "The Waters and Sediments of the Rio Orinoco and its major Tributaries, Venezuela and Colombia." United States Geological Survey water-supply paper, ISSN 0886-9308 /A-B. Washington: United States Government Printing Office.
• Rawlins, C.B. (1999). The Orinoco River. New York: Franklin Watts.
• Triana, S. Pérez. Down the Orinoco in a Canoe
• Weibezahn, F.H., Haymara, A. and M.W. Lewis (1990). The Orinoco River as an ecosystem. Caracas: Universidad Simon Bolivar.

• Church, George Earl (1911). "Orinoco" . Encyclopædia Britannica. Vol. 20 (11th ed.). pp. 275–276.
• Down the Orinoco in a Canoe at Project Gutenberg (Transcription of book from 1902)
• "Rios de Integracion ". Geurgescu, Paul. CAF. 2017