PELJESAC is a peninsula in southern Dalmatia, between the Neretva and Mali Ston channels in the north-east, and the Peljeac and Mljet channels in the south-west, from the isthmus of Ston to Cape Lovie in the north-west.

Limestone crests stretch along the coasts, and between them, in the middle of the island, are sunny sides, ideal for viticulture. The highest peak is Zmijino Brdo (Sveti Ilija, 961 m) (Viper's Hill or St. Elias). The north-eastern coast of the peninsula, exposed to the bora, is colder and drier than the south-western, which is warmer and wetter due to the sirocco.

Major places include Orebic, Trpanj, Viganj, Ston, Janjina, Kuna Peljeska and others; they are located mainly in the interior. Economy is based on farming, viticulture (production of the famous wine sort Dingac, wine-cellars in Potomje and Ston), olive growing, fishing and tourism. The saltworks in Ston are of an enormous importance for the island's economy, as well as the cultivation of molluscs (crustaceans).

The peninsula was populated as early as the prehistoric times (tumuli, remains of a hill-fort above the village of Podvlatica near Orebic). The early Christian and pre-Romanesque periods left more architectural traces in Ston (Our Lady of Luine, St. Michael with wall paintings) and Janjina (St. George).

The Gothic Franciscan monasteries in Ston and Orebic date back to the late Middle Ages, and the fortifications of Ston, one of the largest fortification complexes on the eastern coast of the Adriatic, were built in the period 1333-1613. From the 17th century the economic prosperity of Peljeac was related to the development of shipping, which had a considerable impact on building activities.