The United Nations Convention on the Law of the Sea (UNCLOS) is an international treaty that establishes a comprehensive legal framework for all marine and maritime activities globally. It is often called the "constitution for the oceans" and defines the rights and responsibilities of nations in their use of the world's oceans. The Convention resulted from the third United Nations Conference on the Law of the Sea (UNCLOS III), which took place between 1973 and 1982. It was opened for signature on December 10, 1982, in Montego Bay, Jamaica, and entered into force on November 16, 1994, after Guyana became the 60th nation to ratify it.
The Convention was created to solve the problem of conflicting and expanding national claims over the sea, replacing the older 17th-century concept of "freedom of the seas" where national rights were limited to a narrow belt of water, typically three nautical miles. UNCLOS replaced the four treaties of the 1958 Geneva Conventions on the Law of the Sea and codified customary international maritime law.
The Convention, which contains over 300 Articles grouped into 17 Parts, works by dividing the ocean into five main maritime zones, defining the rights and duties of coastal states in each. A coastal state's sovereignty extends to its Territorial Sea, which can be up to 12 nautical miles from the baseline, including the airspace, seabed, and subsoil. Foreign ships have the right of innocent passage through the Territorial Sea, meaning their passage cannot be prejudicial to the peace, good order, or security of the coastal state. Beyond this is the Contiguous Zone, extending up to 24 nautical miles, where the coastal state can enforce laws regarding customs, fiscal, immigration, and sanitary matters. The Exclusive Economic Zone (EEZ) extends up to 200 nautical miles from the baseline, granting the coastal state sovereign rights for the purpose of exploring, exploiting, conserving, and managing all natural resources, whether living or non-living. The High Seas are all parts of the sea not included in any state's EEZ, Territorial Sea, or internal waters, and are open to all states for freedoms like navigation and overflight. The seabed beyond the continental shelf is called "the Area" and is governed by the principle of the "common heritage of mankind".
UNCLOS connects to several institutions it established, including the International Tribunal for the Law of the Sea (ITLOS) in Hamburg, Germany, for dispute settlement, and the International Seabed Authority (ISA), which administers the resources of the Area. It also connects to the Commission on the Limits of the Continental Shelf (CLCS).
The Convention has been amended and supplemented; the Agreement relating to the implementation of Part XI of the Convention was signed in 1994 to address concerns about deep seabed mining and is interpreted as a single instrument with the original Convention. More recently, in 2023, an agreement was reached on a High Seas Treaty (formally the Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction) to protect ocean life in international waters, which will be added as an instrument of the Convention. In May 2024, ITLOS issued an advisory opinion stating that greenhouse gas emissions constitute marine pollution under UNCLOS.