Marys River is a 40-mile (64 km) tributary of the Willamette River in the U.S. state of Oregon. From its source at the confluence of its east and west forks near Summit, it flows generally southeast from the Central Oregon Coast Range to Corvallis. The West Fork Marys River, which is 6 miles (9.7 km) long, rises at 44°44?00?N 123°34?15?W? / ?44.7333333°N 123.5708333°W? / 44.7333333; -123.5708333? (West Fork Marys River source) and flows south to join the East Fork.[2] The East Fork, which is 5 miles (8.0 km) long, rises at 44°42?00?N 123°30?55?W? / ?44.7°N 123.5152778°W? / 44.7; -123.5152778? (East Fork Marys River source) and flows southwest to join the West Fork.[6]