RIAS can stand for one of the following:

• Rias, the plural of Ria, a lower river valley submerged by the sea.
• RIAS, the Royal Incorporation of Architects in Scotland, a professonal body.
• RIAS, the Rundfunk im amerikanischen Sektor (Radio in the American Sector), a Voice of America-like radio station in West Berlin.
• RIAS, the Recording Industry Association (Singapore)
• RIAS, the Representatives of Internal Audit Services of the United Nations Organizations and Multilateral Financial Institutions