Kocaeli Province

Kocaeli Province (Turkish: Kocaeli ili, pronounced [koˈdʒaeli]) is a province and metropolitan municipality of Turkey and one of only three not to have the same official name as its capital, İzmit, which is thus also sometimes called Kocaeli. Its area is 3,397 km (1,312 sq mi), and its population is 2,102,907 (2023). The province is the successor of the Ottoman-era Sanjak of Kocaeli. The largest towns in the province are İzmit and Gebze. The traffic code is 41.

The province is located at the easternmost end of the Sea of Marmara around the Gulf of İzmit. Kocaeli is bordered by the province of Istanbul and the Marmara Sea to the west, the Black Sea to the north, the province of Sakarya to the east, the province of Bursa to the south and the province of Yalova to the southwest. The metropolitan area of Istanbul extends to the Kocaeli-Istanbul provincial border.