The Ruak River (,, ; น้ำแม่ฮวก, ) is a right hand tributary of the Mekong. The mouth of the Ruak river is at the Thai-Burma border opposite Laos, a spot known as the "Golden Triangle", a popular tourist destination.

Course

The Ruak originates within the hills of the Daen Lao Range, Shan State (Burma), and becomes the boundary river between Thailand and Burma at the confluence with the Mae Sai River near the northernmost point of Thailand. It then meanders eastwards until it empties into the Mekong River at Ban Sop Ruak, Tambon Wiang, Chiang Saen District, Chiang Rai Province. The boundary section of the river is 26.75 km long.