The Nan River is a river in Thailand. It is one of the most important tributaries of the Chao Phraya River. The Nan River originates in the Luang Prabang Range, Nan Province. The provinces along the river after Nan Province are Uttaradit, Phitsanulok and Phichit. The Yom River joins the Nan River at Chum Saeng district, Nakhon Sawan Province. When the Nan river joins together with the Ping River at Pak Nam Pho within the town Nakhon Sawan it becomes the Chao Phraya River.The Nan river runs about 390 miles south.
The chief tributary of the Nan is the Yom River, which joins the Nan within Amphoe Chum Saeng in the Nakhon Sawan Province. Other direct tributaries include the Butsabong and Wang Pong rivers of the lower Nan Basin, the Wat Ta Yom and Wang Thong Rivers which joint he Nan within Phichit Province, the Khwae Noi River which joins the Nan within Phitsanulok Province, the Tron and Pat Rivers, which join the Nan within Uttaradit Province, the Wa, Haet, Pua, Yao and Hao Rivers, which Join the Nan within Nan Province.