Kartepe is a town and district of Kocaeli Province, Turkey.
Kartepe, then known as Köseköy, was founded in 1600s. After the Population exchange between Greece and Turkey agreement, Turks from Greece were settled in Köseköy in 1920s. Later people from Black Sea coast were also settled around Köseköy. Being a part of industrial area the population increased and in 1970 it was declared a seat of township. In 2008 it was merged to nearby towns, renamed as Kartepe and became a district center of Kocaeli Province. The municipality of Kartepe is now an intracity municipality of Greater Kocaeli.