The Biga River () is a small river in ÃÂanakkale Province in northwestern Turkey. The river begins at the base of Mount Ida and trends generally northeasterly to the Sea of Marmara. It is about east of the Dardanelles. It flows past the towns of ÃÂan and Biga and enters the Sea of Marmara at Karabiga. It is also known as the ÃÂan (ÃÂan ÃÂayñ) and the Kocabaà  (Kocabaà  ÃÂayñ).
The Biga was the classical Granicus (, Granikòs Potamós). Cephalon (FGrHist 45 F 5.) wrote that the river named after Graecus (ÃÂÃÂñùúÃÂÃÂ).
The banks near the modern-day town of Biga were the site of the Battle of the Granicus, fought in 334 BC between the Macedonian army of Alexander the Great and the forces of the Persian Empire of Darius III. This was Alexander's first victory over the Persians. In antiquity, the river was described as having strong, turbulent current, with steep banks and varying depth.
There is also a valley named in its honor on Mars. The Granicus Valles is at 29.72ð N, 131.0ð E and runs for .