Sultan Omar Ali Saifuddien Mosque is an Islamic mosque located in Bandar Seri Begawan, the capital of the Sultanate of Brunei. Considered as one of the most beautiful mosques in the Asia Pacific, it is a place of worship for the Muslim community, a major landmark and a tourist attraction of Brunei.

Named after Omar Ali Saifuddien III, the 30th Sultan of Brunei who also initiated its construction, the mosque serves as a symbol of the Islamic faith in Brunei and dominates the skyline of Bandar Seri Begawan. The building was completed in 1958 and is an example of modern Islamic architecture. The mosque unites Mughal architecture and Italian styles. The design was done by A.O.Coltman of the firm Booty and Edwards Chartered Architects, who were based in Kuala Lumpur, Malaysia at that time.

Built in an artificial lagoon on the banks of the Brunei River at Kampong Ayer- the "village in the water", the mosque has marble minarets and golden domes, a courtyard and is surrounded by a large number of trees andfloral gardens. A bridge reaches across the lagoon to Kampong Ayer in the middle of the river. Another marble bridge leads to a structure in the lagoon meant as a replica of a 16th Century Sultan Bolkiah Mahligai Barge. The barge itself was completed in 1967 to commemorate the 1,400th anniversary of Nuzul Al-Quran (coming down of the Quran) and was used to stage the Quran reading competitions.

The mosque's most recognizable feature - the main dome, is covered in pure gold. The mosque stands 52 m (171 ft) high and can be seen from virtually anywhere in Bandar Seri Begawan. The main minaret is the mosque's tallest feature. In a unique way it mixes Renaissance and Italian architectural style. The minaret has an elevator to the top, where a visitor can enjoy a panoramic view of the city.