The Kvarner Gulf (Croatian: Kvarnerski zaljev, Italian: Golfo del Quarnero/Quarnaro/Carnaro; sometimes also Kvarner Bay) is a bay in the northern Adriatic Sea, located between the Istrian peninsula and the northern Croatian seacoast.

The main islands within the Kvarner are Cres, Krk, Pag, Rab and Lošinj. The main portion of the Kvarner bay is that between the mainland, Cres and Krk. A smaller body of water located between Cres, Krk, Rab and Pag is called Kvarnerić (the little Kvarner).

The bay is notable for its depth, which allows for the city of Rijeka at its northernmost point to have a sea port that can handle the largest ships such as tankers.