This list covers 35 rivers with names starting with the letter O, ranging alphabetically from “Ob” to “Oostanaula”. They span every inhabited continent, from Arctic giants in Siberia to short coastal streams in Europe and blackwater rivers in the American South. Many of these rivers carry drinking water, support farming, generate hydroelectric power, and shape the borders and history of the countries they pass through.

Rivers are natural channels of flowing water that carry rain, snowmelt, and groundwater from higher ground down to a lake, sea, or ocean. Some, like Russia’s Ob, stretch for thousands of kilometers and drain entire regions, while others, like the Oostanaula in Georgia, run just a short distance before joining a larger river. One of the more unusual entries, the Okavango, never reaches the sea at all — it spreads into a vast inland delta in Botswana that supports one of Africa’s richest wildlife habitats.

Below you’ll find the table with each river’s name, countries, length, type, and description.

River: the name of the river, so you can quickly identify and look up the one you’re interested in.

Countries: the country or countries the river flows through, useful for understanding its geographic and political reach.

Length (km): the river’s total length in kilometers, giving you a quick sense of its scale.

Type: whether the river is a major waterway, a tributary of a larger river, an independent river reaching the sea on its own, or an endorheic river with no outlet.

Description: a short summary of the river’s route, significance, and any notable historical or cultural details worth knowing.

Rivers

Descriptions