The Berdan the ancient Cydnus (Ancient Greek: Κύδνος, romanized: Kúdnos), is a river in Mersin Province, south Turkey. The historical city of Tarsus is on the river and it is therefore sometimes called the Tarsus River. Originally the watercourse passed directly through the city, but the section in Tarsus was changed to its present course in the 6th century. The river is also the location of Tarsus Waterfall.
The main headwaters are in the Toros Mountains. There are two main tributaries: Kadıncık and Pamukluk. Total length of the river is 124 kilometres (including Kadıncık). Although the river is quite short, the average discharge is 42 cubic metres per second, which is higher than most short rivers in the vicinity. The drainage basin covers 1,592 square kilometres. Just north of Tarsus there is a waterfall on the river, which is a popular picnic area for Tarsus residents.
There are four dams on Berdan.
