MSSB may refer to:
MacArthur Story Stem Battery (MSSB), a form of psychological testing Metropolitan Separate School Board, the former name for the Toronto Catholic District School Board from 1953–1998 Missile Servicing and Storage Building (MSSB), a specialist building at RAF Scampton in the 1950s Morgan Stanley Smith Barney, the broker-retailer division of Morgan Stanley Modified Statutory Solvency Basis (MSSB), an actuarial method of Deferred Acquisition Costs in the insurance industry