Halkidhiki is a peninsula and regional unit of Greece, part of the Region of Central Macedonia, in the geographic region of Macedonia in Northern Greece. The autonomous Mount Athos region constitutes the easternmost part of the peninsula, but not of the regional unit.

The capital of Halkidiki is the main town of Polygyros, located in the centre of the peninsula. Chalkidiki is a popular summer tourist destination.

The Cholomontas mountains lie in the north-central part of Chalkidiki. Chalkidiki consists of a large peninsula in the northwestern Aegean Sea, resembling a hand with three 'fingers' (though in Greek these peninsulas are often referred to as 'legs'). From west to east, these are Kassandra, Sithonia, and Mount Athos, a special polity within Greece known for its monasteries. These "fingers" are separated by two gulfs, the Toronean Gulf and the Singitic Gulf. The Chalkidiki borders on the regional unit of Thessaloniki to the north, and is bounded by the Thermaic Gulf on the west and the Strymonian Gulf on the east.

There are several summer resorts on the beaches of all three fingers where other minor towns and villages are located, such as at Yerakini (Gerakina Beach), Neos Marmaras (Porto Carras), Ouranoupolis, Nikiti, Psakoudia, Kallithea (Pallene/Pallini, Athos), and more.