Laos is predominantly Theravada Buddhist, with Pew Research estimating roughly two-thirds of the population as Buddhist, alongside animist and ancestor-venerating traditions practiced especially among highland ethnic minorities such as the Hmong and Khmu, who follow indigenous spirit religions often blended with or distinct from lowland Lao Buddhism.
Buddhism reached the Lao kingdom of Lan Xang by the fourteenth century, becoming the state religion under King Fa Ngum and his successors, who built major stupas including That Luang in Vientiane, the country's most important national and religious monument, said to enshrine a relic of the Buddha. French colonial rule from the late nineteenth century introduced a small Catholic minority, concentrated among Vietnamese immigrant communities, while the communist Pathet Lao's 1975 victory ended the monarchy and placed all religious institutions, including the Buddhist sangha, under state oversight through the Lao Front for National Construction. Village-level spirit cults, particularly the propitiation of phi spirits, continue alongside Buddhist practice in a pattern common across mainland Southeast Asia, and Christian minorities face significant restriction, especially in rural highland areas where evangelical growth among ethnic minorities has drawn government suspicion.