| Mueang Trat River | |
| Name Other: | Trat River, Khao Saming River, Khlong Khao Saming, Khlong Yai |
| Subdivision Type1: | Country |
| Subdivision Name1: |  Thailand |
| Subdivision Type2: | Province |
| Subdivision Name2: | Trat |
| Length: | 55km (34miles) |
| Source1: | Confluence of Khlong Sato and Khlong Ang |
| Source1 Location: | Bo Phloi, Bo Rai and Sato with Wang Takhian, Khao Saming |
| Source1 Coordinates: | 12.4933°N 102.4831°W |
| Mouth: | Ao Trat |
| Mouth Location: | Nong Khan Song and Tha Phrik, Mueang Trat |
| Mouth Coordinates: | 12.1906°N 102.5708°W |
| River System: | East coast basin |
Mueang Trat River (th|แม่น้ำเมืองตราด, pronounced as /th/), or just called Trat River (แม่น้ำตราด, pronounced as /th/) is the longest and largest river in Trat province, eastern Thailand.
It originated from the canals Khlong Sato and Khlong Ang, which receive water from the Banthat range, flowing together at the border Bo Rai and Khao Saming districts. Then flows south passing through Khao Saming district to the southeast entering Mueang Trat district passing through the downtown Trat before empties to Ao Trat, part of the Gulf of Thailand. It is approximately 551NaN1 long.[1]
As it flows through Khao Saming district, it is called Khao Saming River (แม่น้ำเขาสมิง, pronounced as /th/), otherwise known as Khlong Khao Saming (คลองเขาสมิง, pronounced as /th/) or Khlong Yai (คลองใหญ่, pronounced as /th/).[2]
The water in the Trat river in the phase of the Khao Saming river is murky red and flows rapidly. In 1931, it was also recorded as the first place in Thailand where an Asian arowana, a rare species living fossil fish was caught for the first time by a local boy scout. The caught fish was 26 cm long and specimen were sent to Bangkok for species identification.[3] Currently, believed to have been locally extinct.[4]
Mueang Trat river is an important transportation route from the past to the present. In the area of Mueang Trat, there were junks that sailed in and docked to pick up and deliver goods. At present, there are many ports along the river where fishing boats congregate along the jetty.[5]