BS 10, a historic British standard (by BSI Group), specifies dimensions, materials, and pressure ratings for pipe flanges and flanged fittings. It covers multiple flange types (e.g., welding neck, slip-on, blind) and sizes, using PN (Pressure Nominal) and old Class ratings for pressure definition.

Once widely used in the UK and Commonwealth nations for industries like oil, gas, and water, it has gradually been superseded by EN standards (e.g., EN 1092-1) in the EU and UK post-Brexit. However, BS 10 still remains relevant for maintaining legacy piping systems, ensuring interchangeability and safety for existing flanged connections.