The Yom River () is the main tributary of the Nan River (which itself is a tributary of the Chao Phraya River). The Yom originates in Pong district, Phayao Province. Outing Phayao, it flows through Phrae and Sukhothai as the main water resource of the both provinces before it tributes the Nan River at Chum Saeng district, Nakhon Sawan Province.

Tributaries

Tributaries of the Yom include Pong, Ngao, Ngim, Sin, Suat, Pi, Mok, Phuak, Ramphan, Lai, Khuan and Kam Mi Rivers.

Yom Basin

The Yom river and its tributaries drain a total area of 23,616 km² of land (called the Yom Basin) in the provinces of Sukhothai, Phitsanulok, Phichit, Phrae and Lampang.

The Yom Basin is part of the Greater Nan Basin and the Chao Phraya Watershed.

National Parks

The Yom River flows through Mae Yom National Park in Phrae Province.