The Mun River (Thai: แม่น้ำมูล, RTGS: Maenam Mun, pronounced [mɛ̂ː.náːm mūːn]; Northeastern Thai: แม่น้ำมูล, pronounced [mɛ̄ː.ːnâːm mu᷇ːn]), sometimes spelled Moon River, is a tributary of the Mekong River. It carries approximately 26 cubic kilometres (6.2 cu mi) of water per year.

The river begins in the Khao Yai National Park area of the Sankamphaeng Range, near Nakhon Ratchasima in northeast Thailand. It flows east through the Khorat Plateau in southern Isan (Nakhon Ratchasima, Buriram, Surin, and Sisaket Provinces) for 750 kilometres (466 mi), until it joins the Mekong at Khong Chiam in Ubon Ratchathani. The Mun River's main tributary is the Chi River, which joins it in the Kanthararom District of Sisaket Province.

Thanks to the Andy Williams hit song, the Mun River was called "Moon River" by US Air Force personnel stationed at Ubon Ratchathani airbase during the Vietnam War. The spelling is still fairly common.

The controversial Pak Mun Dam, which is charged with causing environmental damage, is near the river's confluence with the Mekong.

• Lam Dom Noi
• Chi River
• Lam Takhong

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• Seriprachathippatai 2497 Bridge

Media related to Mun River at Wikimedia Commons