Does the Irrawaddy River flow outside Myanmar?

No, the Irrawaddy River does not flow outside of Myanmar. It runs entirely within the territory of the country, serving as its principal river and most important commercial waterway.1

While the river is formed by the confluence of the Nmai and Mali rivers, both of which originate in the mountains of northern Myanmar, the Nmai River rises in a glacier on the border with Tibet (China). However, the Irrawaddy itself remains contained within Myanmar throughout its entire course as it flows southward to the Andaman Sea.21