| Yom River | |
| Name Other: | แม่น้ำยม |
| Map: | Chaophrayarivermap.png |
| Subdivision Type1: | Country |
| Subdivision Name1: | Thailand |
| Length: | 700km (400miles) [1] |
| Discharge1 Location: | Nakhon Sawan |
| Discharge1 Avg: | 103m3/s |
| Discharge1 Max: | 1916m3/s |
| Source1 Location: | Bun Yuen village, Pong district, Phi Pan Nam Range, Phayao Province |
| Source1 Elevation: | 347m (1,138feet) |
| Mouth: | Nan River |
| Mouth Location: | Chum Saeng district, Nakhon Sawan province |
| Mouth Elevation: | 28m (92feet) |
| Basin Size: | 24047km2 |
| Tributaries Right: | Ngao River |
The Yom River (th|แม่น้ำยม,, pronounced as /th/; nod|น้ำแม่ยม, pronounced as /náːm mɛ̂ː.ɲōm/) is a river in Thailand. It is the main tributary of the Nan River (which itself is a tributary of the Chao Phraya River). The Yom River has its source in the Phi Pan Nam Range in Pong District, Phayao Province. Leaving Phayao, it flows through the Phrae and Sukhothai provinces as the main water resource of both provinces before it joins the Nan River at Chum Saeng District, Nakhon Sawan Province.
See main article: Tributaries of the Chao Phraya River. Tributaries of the Yom include the Nam Mae Phong, Ngao River, Nam Ngim, Huai Mae Sin, Nam Suat, Nam Pi, Mae Mok, Huai Mae Phuak, Mae Ramphan, Nam Mae Lai, Nam Khuan, and Nam Mae Kham Mi.
The Yom river and its tributaries drain a total area of 24047km2 of land (called the Yom Basin) in the provinces of Sukhothai, Phitsanulok, Phichit, Phrae, and Lampang.[2] The Yom Basin is part of the Greater Nan Basin and the Chao Phraya Watershed.
A controversial large dam was planned on the Yom River in the central area of the Phi Pan Nam mountains in Kaeng Suea Ten in 1991 but the project was later abandoned.[3] The debate about the dam was opened again in 2011.[4] Currently a proposal is being debated to build two smaller dams on the Yom River in the area instead of the Kaeng Suea Ten mega-dam.[5]
The Yom River flows through Mae Yom National Park in Phrae Province.