East Siberian Sea (Russian: ) is a marginal sea in the Arctic Ocean. It is located between the Arctic cape in the North, the coast of Siberia in the South, the New Siberian Islands in the West and Wrangel Island in the East, bordering on the Laptev Sea and Chukchi Sea.

The area of the sea is 913,000 km²; most of the time it is covered with ice. 70% of it is no deeper than 50m, the deepest point being 155m. The coast is mostly flat in the West (up to the mouth of the Kolyma), mountainous in the East. Average temperatures (air) is 0°C to 2°C (4°C in the South) in the summer, reaching -30°C in the winter.

The sea was navigated by Russian sea-farers, moving from one river mouth to another in their kochs as early as the 17th century. In 1648 Semyon Dezhnev and Fedot Alekseev sailed the coast from the Kolyma to river Anadyr and Bering Strait. Systematic exploration and mapping of the sea and its coasts was carried out by a series of expeditions in 1735-42, 1820-24, 1822, 1909, 1911-14.

Principal port is Pevek. (see also: Northern Sea Route)