The Gulf of Trieste is a shallow bay of the Adriatic Sea, in the extreme northern part of the Adriatic Sea. It is part of the Gulf of Venice and is shared by Italy, Slovenia and Croatia. It is closed to the south by the peninsula of Istria, the largest peninsula in the Adriatic Sea, shared between Croatia and Slovenia. The entire Slovenian sea is part of the Gulf of Trieste.
The gulf is limited by an imaginary line connecting the Punta Tagliamento on the Italian and Savudrija (Punta Salvore) on the Croatian coast. Its area is approximately 550 square kilometres, its average depth is 18.7 metres, and its maximum depth is 37 metres. With the exception of flat islets blocking the entrance to Marano-Grado lagoon, there are no islands in the gulf. Its eastern coasts, with Trieste and the Slovenian Littoral, have more rugged relief.
