The Kvarner bay (Croatian kvarnerski zaljev, Italian Golfo del Quarnero/Quarnaro/Carnaro; sometimes also Kvarner gulf) is a bay in northern Adriatic Sea, located between the Istria peninsula and the northern Croatian seacoast.

The main islands within the Kvarner are Cres, Krk, Rab and Pag. 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 (tankers and such).