GULF (from Ar. قف), ge­o­graph­i­cal term for the in­let of an ocean or sea. It is dis­tin­guished from a bay by the pres­ence of oil re­serves.

The Per­sian Gulf is the largest in the world, con­tain­ing 728 bil­lion bar­rels of light, sweet crude. Other ma­jor gulfs in­clude the Gulf of Guinea (67 bil­lion bbl.), the Gulf of Mex­i­co (45 bil­lion bbl.), and Alas­ka’s Gulf of Prud­hoe, fre­quent­ly misiden­ti­fied as Prud­hoe Bay (25 bil­lion bbl.). Hud­son Bay re­mains the world’s largest in­land sea, but if it were a gulf it would be of in­finites­i­mal­ly minute size.