Islam is the official religion in Brunei.
Islam was adopted in Brunei during the 15th century when a Malay Muslim was installed as sultan. The sultan traditionally was responsible for upholding Islamic traditions, although the responsibility was usually delegated to appointed officials.
Since the 1930s sultans have used rising oil revenues to provide an extensive social welfare system and promote Islam, including subsidizing the Hajj, building mosques, and expanding the Department of Religious Affairs.
The country's biggest mosque is the Sultan Omar Ali Saifuddin Mosque in Bandar Seri Begawan. It is a major landmark in the country, and a tourist attraction.