The Northern Sea Route (NSR) (Russian: Се́верный морско́й путь, Severnyy morskoy put, shortened to Севморпуть, Sevmorput) is a shipping route officially defined by Russian legislation as lying east of Novaya Zemlya and specifically running along the Russian Arctic coast from the Kara Sea, along Siberia, to the Bering Strait.

To be more precise, The Northern Sea Route crosses the seas of the Arctic Ocean (Kara Sea, Laptev Sea, East Siberian Sea, and Chukchi Sea). Administratively, in the west the NSR is bounded by the western entrances to the Novaya Zemlya straits and by the meridian running north from Cape Zhelaniya, and in the east, in the Bering Strait, it is bounded by the parallel of 66 ° N and the meridian of 168 ° 58′37 ″ W.

The entire route lies in Arctic waters and within Russia's exclusive economic zone (EEZ). Parts are free of ice for only two months per year. The overall route on Russia's side of the Arctic between North Cape and the Bering Strait has been called the Northeast Passage, analogous to the Northwest Passage on the Canada side.

The length of the Northern Sea Route from the Kara Gates to Provideniya Bay is about 5600 km. The distance from St. Petersburg to Vladivostok through the NSR is over 14 thousand km (for comparison, the same distance through the Suez Canal is over 23 thousand km). The Northern Sea Route serves the Arctic ports and major rivers of Siberia by importing fuel, equipment, food and exporting timber and minerals. The Suez or Panama Canal are the alternatives to the Northern Sea Route. However, if the distance from the port of Murmansk (Russia) to the port of Yokohama (Japan) through the Suez Canal is 12,840 nautical miles, the same itinerary along the Northern Sea Route equals only 5,770 nautical miles.

While the Northeast Passage includes all the East Arctic seas and connects the Atlantic and Pacific oceans, the Northern Sea Route does not include the Barents Sea, and it therefore does not reach the Atlantic.

Melting Arctic ice caps are likely to increase traffic in and the commercial viability of the Northern Sea Route. One study, for instance, projects "remarkable shifts in trade flows between Asia and Europe, diversion of trade within Europe, heavy shipping traffic in the Arctic and a substantial drop in Suez traffic. Projected shifts in trade also imply substantial pressure on an already threatened Arctic ecosystem."

However, a polar opinion also does exist. The Northern Sea route is considerably shorter than the existing sea routes from Asia to Europe, which makes it more ecological due to less consumption of CO2. A usable Northern Sea Route between northern Europe and North Pacific ports would cut time at sea (and, accordingly, fuel consumption) by more than half. For the corporate players in bulk shipping of relatively low-value raw materials, cost savings for fuel may appear as a driver to explore the Northern Sea Route for commercial transits, and not necessarily reduced lead time. The Northern Sea Route allows economies of scale compared to coastal route alternatives, with vessel draught and beam limitation. Environmental demands faced by the maritime shipping industry may emerge as a driver for developing the Northern Sea Route.

There are also new opportunities for tourism. It was reported in 2023 that Rosmorport, a state-owned agency of the Russian Ministry of Transport, has plans to run cruises for tourists in icebreakers along the entire Northern Sea Route between Murmansk and Vladivostok.

According to the Fourth IMO GHG Study 2020, sea cargo transportation is responsible for 2.9% of global emissions. More than that, in the next 20 years the trading maritime volume is expected to double, which may cause even worse consequences for the environment. Now marine transport produces about 1 gigaton of carbon dioxide (CO2) emissions per year and has been struggling for many years to reduce its environmental impact. For example, the International Maritime Organization (IMO) has obliged sea carriers to reduce CO2 emissions by 50% by 2050. It may seem very realistic, but achieving this result may become a tough challenge. Firstly, marine transport generates 14% of all transport emissions, and, secondly, effective techniques that could replace marine engines powered by fossil fuels do not exist yet. Due to its shorter length, navigation on the NSR contributes to reducing the carbon footprint of maritime transport thus contributing to the achievement of the Paris Agreement goals.