The term marginal sea commonly has two differing meanings.
As an oceanographic term, marginal sea indicates a partially enclosed sea adjacent to or widely open to the open ocean at the surface, but bounded by submarine ridges on the sea floor.[clarification needed]
As a geopolitical term, marginal sea is equivalent to territorial waters. Defining what naval territory falls under a state's jurisdiction as "marginal sea" is important in determining what maritime resources that state can exploit.
Marginal seas of the world 
Sources differ over which seas are considered marginal seas as well as which ocean a given sea is considered a marginal part of. There is no single ultimate authority on the matter.
Marginal seas of the Arctic Ocean:
- Barents Sea
- Beaufort Sea
- Chukchi Sea (separated by Wrangel Island)
- Kara Sea
- Laptev Sea (separated by the Severnaya Zemlya and the New Siberian Islands)
Marginal seas of the Atlantic Ocean:
- Argentine Sea
- Baltic Sea
- Caribbean Sea
- English Channel
- Gulf of Mexico
- Hudson Bay
- Irish Sea (separated by Ireland)
- Mediterranean Sea
- North Sea (by Great Britain)
- Norwegian Sea (by Iceland, the Faroe Islands, and Shetland); and Greenland Sea
- Scotia Sea (by the Falkland Islands, South Georgia, and the South Sandwich Islands)
- Sometimes the Arctic Ocean itself is considered a marginal sea of the Atlantic.
Marginal seas of the Indian Ocean:
- Andaman Sea (separated by the Andaman and Nicobar Islands).
- Arabian Sea
- Bay of Bengal
- Java Sea (separated by the Greater Sunda Islands)
- Persian Gulf
- Red Sea
- Sea of Zanj (an historic entity off the southeast African coast and including the Mascarene islands)
Marginal seas of the Mediterranean Sea:
- Adriatic Sea
- Aegean Sea
- Alboran Sea
- Balearic Sea
- Black Sea
- Sea of Crete
- Ionian Sea
- Ligurian Sea
- Myrtoan Sea
- Thracian Sea
- Tyrrhenian Sea
Marginal sea of the Black Sea:
Marginal seas of the Pacific Ocean:
- Bering Sea (separated by the Aleutian Islands)
- Celebes Sea
- Coral Sea (by the Solomon Islands and Vanuatu).
- East China Sea (by the Ryukyu Islands)
- Philippine Sea (by the Ogasawara Islands, the Mariana Islands, and Palau)
- Sea of Chiloé (by Chiloé Island, Chile)
- Sea of Japan (by the Japanese Archipelago)
- Sea of Okhotsk (by the Kurile Islands and Kamchatka Peninsula)
- South China Sea (by the Philippines)
- Sulu Sea
- Tasman Sea (between Australia and New Zealand)
- Yellow Sea (by the Korean Peninsula)
Marginal seas of the Southern Ocean:
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- American Congress on Surveying and Mapping (1994). Glossary of the mapping sciences. ASCE Publications. p. 469. ISBN 978-0-7844-0050-0. Retrieved 9 December 2010.
- George M. Cole (21 March 1997). Water boundaries. John Wiley and Sons. pp. 137–139. ISBN 978-0-471-17929-0. Retrieved 9 December 2010.
- James C. F. Wang (1992). Handbook on ocean politics & law. Greenwood Publishing Group. pp. 14–. ISBN 978-0-313-26434-4. Retrieved 9 December 2010.
- Kara Sea, Encyclopædia Britannica
- Laptev Sea, Encyclopædia Britannica
- Longhurt, Alan R. (2007). Ecological Geography of the Sea. Academic Press. p. 104. ISBN 978-0-12-455521-1. Retrieved 13 December 2010.
- Andaman Sea, Encyclopædia Britannica