The bases of the Bruneian monarchy are to be sought at the core of the royal institution: the coronation ritual. The sources (from the start of the 18th century to the start of the 21st century) show a ritual structured in three stages: 1°) preliminaries; 2°) coronation; 3°) closing ceremonies. The comparison with Siam highlights both the Brahmanic dimension of the Bruneian rite and its Malay and Javanese specificities. Remain however beyond this Indianized framework both the opening ritual for the convocation of the ancestors and the presence of the Sakai, whom the myth of foundation installs in position of elders. The Bruneian crown, which belongs to Culture, can thus function only if it is legitimated by the guardians of the Sea, who belongs to Nature.