Phu That Stupa (or the Xaymungkhun Ratanamingmuang Stupa) is the most prominent hill top stupa in Oudomxay, located in the center of the Muang Xay town. The stupa was built to allow all people of the region to come together to celebrate religious festivals and tradition (give alms to the monks, purify themselves, make offerings to ancestors, etc.). Religious celebrations on every full moon day are held at the stupa.

It is presumed that the 600-year-old stupa was originally built by Tai Leuduring the time when Xaysettha was King of Laos. The stupa measures 18m by 18m by 18m, and is also known as "the symbol of Oudomxay".