Comprehensive, detailed and reliable data on marine energy resource characteristics is essential for advancing the marine renewable energy industry. In this paper, we showcase the U.S. Department of Energy’s resource characterization and assessment project. This multi-year project, conducted by three national labs, is delivering data and results designed to reduce the uncertainty, risk, and cost of marine energy technology. Over its first three years this project has: 1) completed highresolution, long-term regional wave hindcasts for the U.S. west coast, east coast, and Alaska, 2) completed highresolution tidal models of five top-ranking tidal energy sites, 3) completed resource measurements following International Electrotechnical Commission (IEC) technical specifications at four wave energy sites and four tidal energy sites, and 4) developed wave classification schemes. The project has been guided by an international steering committee composed of industry partners and academic experts. As the project moves toward completion the team will: complete high-resolution modelling for all U.S. coastal waters, complete resource measurements at top-ranking sites, refine the national resource assessments, propose classification schemes to the IEC standards body, and upgrade the Marine and Hydrokinetic (MHK) Atlas to make the project’s data public and accessible. These data and tools can be used for: device design processes for technology developers, economic assessments for project developers, energy assessments (power supply and energy portfolio diversification) for regional planners and policy makers, operational reliability and economic assessments for utilities and investors, and baseline data for environmental impacts studies needed by regulatory agencies.