Biga Çayı or Kocabaş Çayı (Ancient name;Granicus River) is a small water flow in northwestern Turkey. The flow begins at the base of the Mount Ia and trends generally northeasterly to the Sea of Marmara. It is located approximately 50 km to the east of the Çanakkale boğazı (Çanakkale strait, formerly known as the Dardanelles).