Corinthia borders on Achaea to the west and southwest, the Gulf of Corinth and Attica to the north, the Saronic Gulf to the east, Argolis to the south and Arcadia to the southwest.
The Corinth Canal, carrying ship traffic between the Ionian and the Aegean seas, is about 4 km east of Corinth, cutting through the Isthmus of Corinth. Corinthia is increasingly seen as part of the wider metropolitan area of Athens, with municipalities, such as Agioi Theodoroi in the easternmost part of the regional unit, being considered suburbs of Athens.
The area around Corinth and the western Saronic including the southeastern part are made up of fault lines including the Corinth Fault, the Poseidon Fault and a fault running from Perahcora to Agioi Theodoroi. More faults are near Kiras Vrysi and Sofiko.
The eastern coastlands of Corinthia are made up of pastures and farmlands where olives, grapes, tomatoes and vegetables are cultivated. The rest of Corinthia is mountainous. Its tallest mountain is Kyllini in its west and the largest lake is Lake Stymphalos, (important in Greek mythology and a bird resort, protected by Natura 2000) situated in the southwest. The reservoir will become one of the largest lakes after its completion.
The climate of Corinthia consists of hot summers and mild winters in the coastal areas and somewhat colder winters with occasional snowfalls in the mountainous areas.
