The Tama River is a major river in Yamanashi, Kanagawa and Tokyo Prefectures on Honshū, Japan. It is officially classified as a Class 1 river by the Japanese government.

Its total length is 138 km, about 85.75 miles, and the total of the river's basin area spans 1.240 km², more than 770 square miles.

The river flows through Tokyo, on the dividing line between Tokyo and Kanagawa. In the city, its banks are lined with parks and sports fields, making the river a popular picnic spot.