The shelf is an underwater extension of the mainland (mainland shoal) at depths of up to 200 metres.

The flattened part of the underwater edge of the continents, adjacent to the land coasts and characterised by a common geological structure. The depth of the shelf edge is usually 100-200 m, but in some cases it reaches 1500-2000 m (for example, in the South Kuril Basin of the Okhotsk Sea); the width is up to 1500 km (for example, in the North Arctic Ocean). The total area of the shelf is about 32 million km2. Oil and gas fields are being developed within the shelf, and the possibility of extracting some other minerals is being investigated. Fishing in the offshore waters is 92%. The shelf is subject to the sovereign rights of the coastal state; no one has the right to develop, explore and exploit the natural resources of the shelf without its direct consent. 

In international law, the continental shelf is the seabed and subsoil of submarine areas extending beyond territorial waters. The legal regime of the continental shelf and its boundaries is governed by the 1982 UN Convention on the Law of the Sea, conventions and national laws.