Halki is a Greek island and municipality in the Dodecanese archipelago in the Aegean Sea, some 9 km (6 mi) west of Rhodes. With an area of 28 km2 (11 sq mi), it is the smallest inhabited island of the Dodecanese. It is part of the Rhodes regional unit. It has a permanent population of 330, concentrated in the only village of Emporio. The 2021 census showed a population of 475 inhabitants. The community is divided in two parts, Chorio and Emporio.

The Dodecanese are a group of 15 larger and 150 smaller Greek islands in the southeastern Aegean Sea and Eastern Mediterranean, off the coast of Turkey's Anatolia, of which 26 are inhabited. This island group generally defines the eastern limit of the Sea of Crete. They belong to the wider Southern Sporades island group.