Wat That Luang Rasamahavihane is known as the "Monastery of the Royal Stupa." It has long been associated with Lao royalty of Luang Prabang. Legend suggests that an early monastery on the site originated from a visit by Buddhist missionaries sent by Asoka, the 3rd-century-B.C. Buddhist evangelical Indian king. The legend is unsupported by any real evidence however. Relics from the early 12th century have been discovered, though they may have come from a site in northern Thailand.

The present sim was constructed on a small hill south of the city in 1818 during the reign of King Manthaturat (1817-36). It may have been built partly from the branches of a bodhi tree located near Wat Keo Fa. The sim is built in Lao style with gables on both the northeast and southwest sides. There are no porches or verandas, nor are there the sweeping rooflines that you find on so many wats in Luang Prabang. The large bronze-and-gilded Buddha inside the sim was transferred from the now-defunct Wat Aham Mungkhun, located a short distance from That Luang. It weighs about 1,100 pounds.

That Luang has long been one of the important ritual sites for Buddhist, traditional, and royal events; the Festival of the 12th month, or Tat, in particular. In the past it was presided over by the king. There are two large stupas on the grounds. The golden funerary stupa in front of the sim contains the ashes of the king, Sisivang Vong (1904-59). It is the site of annual commemorations. There are also a number of smaller stupas that contain the ashes of other kings, members of the royal family, and a mixture of dignitaries. The wat is home to one of the city's larger communities of monks and novices.