Thermaic Gulf

Old French map of the Gulf, 1764.

View of Thermaic Gulf from Peraia, Thessaloniki.

The Thermaic Gulf (Greek: Θερμαϊκός Κόλπος) is a gulf of the Aegean Sea located immediately south of the Thessaloniki regional unit, east of Pieria and Imathia, and west of Chalkidiki. It was named after the ancient town of Therma, which was situated on the northeast coast of the gulf (Therma was later renamed Thessalonica). Near Thessaloniki, the length (north-south) of the gulf is about 100 km, while its width (east-west) is about 5 km. The length of the gulf in its northern part (from its northern extent down to "megalo emvolo" cape) is estimated to stretch 15 km, while after "megalo emvolo" cape towards the south, its length extents a further 50 km. Cape Kassandra lies to the southeast end of the gulf.

To the Romans, the gulf was also known as Thermaicus or Thermaeus sinus ("Gulf of Therma") and as Macedonicus sinus ("The Gulf of Macedon", or "The Macedonian Gulf"). One of its modern names is the "Gulf of Salonica", named after the city of Thessaloniki which sprawls around and along the northeastern coast of the gulf.

Places that lie by the gulf include Sani, Kassandreia, ancient Potidaea, Nea Moudania, Agia Triada, Neoi Epivates, Peraia, Kalochori, Methoni, Pydna, Paralia Katerinis and Olympiaki Akti. The rivers emptying into the gulf are the Pineios, Aliakmon, Loudias, Gallikos and Axios; several streams including one near Pydna also empty into the gulf. The Thermaic Gulf was significantly larger in classical times, with many ancient seaside cities (e.g. Pella) now found several kilometers inland. The extensive silting mainly affects the northern and western parts of the gulf, which receive the bulk of alluvial outflow. The gulf is home to a large number of famous, pristine beaches, which include Sani Beach. However, there are no beaches on the northwest coast, where wetlands stretch from Methone (northwest coast) to Thessaloniki's western suburb of Kalochori.

The Port of Thessaloniki is the gulf's largest and busiest port, while another twelve small ports provide sea transport in, out and around the Thermaic gulf. Major road networks of northern Greece such as the A1/E75 motorway (Athens - Lamia - Thessaloniki) encircles the western portion of the gulf, while the A25 (Thessaloniki - Nea Moudania motorway) almost encircles the eastern part of it.