In Classical Antiquity, Peraia (also referred to as Peraea or Peræa) was a term used to describe a community's territory located "opposite" its primary location. This typically referred to mainland possessions held by an island state. Various historical examples exist, including the peraia of Mytilene, which consisted of coastal towns from the mouth of the Hellespont to the Bay of Adramyttium, and the Rhodian Peraia in southwestern Asia Minor, which covered parts of Caria, Lycia, and other regions between the 5th and 1st centuries BC.
Other notable territories designated as peraia included those belonging to Samos, Samothrace, Tenedos, and Thasos. These possessions were often located on opposite coasts or along specific stretches of the mainland. Additionally, the Perachora peninsula in Greece derived its name from its position across from Corinth. The term was also used generically for the post-1204 Crimean possessions of the Empire of Trebizond.
The name is also associated with Perea (or Peraea), a region that was part of the Herodian Kingdom and is located in modern-day Jordan. In some contexts, such as the city of Myus, the status of being a peraia was a point of dispute between neighboring powers like Miletus and Magnesia.