The Marine Renewable Energy Strategic Framework (MRESF) project has investigated the potential marine renewable energy tidal and wave resource of Welsh waters and considered potential scenarios for the sustainable development of that resource primarily as an aid to policy development and also an indicator of resource for potential developers. This dataset represents the areas with most potential for tidal stream energy development in Welsh waters, as identified by RPS in the Marine Renewable Energy Strategic Framework (MRESF). Device requirements applied include maximum distance from shore (5 km), minimum peak tidal current velocity (1.5 m/s) and depth (10-120 m).