Son, also known by the name Sone River, the main southern tributary of the Ganges
, is a river of central India. It originates from the Amarkantak hills of the Bastar Plateau of Madhya Pradesh
and flows north-west through hills and reaches the Kaimur range, which forms the southern wall of the Gangetic plain (the flood-plain of the Ganges), in Bihar
. From there, the river turns east and continues its flow in that direction until it meets with the Ganges near Patna
after a total course of 465 m.