Kocaeli Subregion

The Kocaeli Subregion (Turkish: Kocaeli Alt Bölgesi) (TR42) is a statistical subregion in Turkey.

Provinces

 * Kocaeli Province (TR421)
 * Sakarya Province (TR422)
 * Düzce Province (TR423)
 * Bolu Province (TR424)
 * Yalova Province (TR425)