It originates at Icalma and Galletué lakes in the Andes and flows 380 kilometres (236 mi) to the Gulf of Arauco (in Spanish) on the Pacific Ocean.

Just downstream from the confluence with the Rahue, the upper course of the river-locally known as Alto Bío Bío-begins to run rapidly through a narrow valley surrounded by mountains, the path becoming increasingly sloped.

From here, the river follows its course increasing its width considerably, reaching 2 kilometres (1.25 mi) wide at its mouth on Pacific Ocean, near San Pedro de la Paz, Gran Concepción.

In the early 1980s, it was renowned as being one of the world's best whitewater rafting venues, with a trip that lasted seven days through some of Chile's wilderness areas.

Endesa, the Chilean state-run power company at that time, constructed the Pangue Dam, despite strong protests by environmentalists.

With the loss of the whitewater rafting venue, displacement of indigenous Pehuenche people, who had lived in the area for centuries, also occurred.