Aksu is one of the main water streams of Giresun Province in the eastern Black Sea Region of Turkey.

Aksu Deresi rises in Karagöl, a rural highland area located very near to provincial borders of Giresun, Ordu and Sivas provinces.

Karagöl is a chain of mountains which is part of the Giresun mountains, in the south of Dereli district of Giresun, and its summit is 3107 meters high.

There is a crater lake on its summit, at 3,107 metres (10,194 ft) above sea level.

The Aksu creek flows down to the Black Sea passing Kızıltaş, Sarıyakup, Pınarlar [tr] and Güdül villages.