Ocean wave energy represents one of the most promising yet underutilized renewable energy resources available globally. This chapter establishes the essential theoretical and practical frameworks for understanding wave energy fundamentals and quantification methods necessary for effective wave farm design. Drawing from oceanography, fluid dynamics, and renewable energy engineering, it presents wave energy as a concentrated form of solar energy transferred through wind interactions with the ocean surface, resulting in a resource characterized by high energy density, relative predictability, and minimal environmental footprint compared to other renewable technologies. The chapter is structured to provide comprehensive coverage across four interconnected sections. The introduction to wave energy offers historical context and basic principles, positioning this resource within the broader renewable energy landscape while explaining the physical mechanisms of wave formation and energy transport. The wave energy potential assessment section examines global and regional resource distribution, detailing measurement technologies and characterization parameters including significant wave height, energy period, directional properties, and seasonal variations essential for site selection. Wave energy calculation methods form the technical core, presenting both linear wave theory and spectral analysis techniques for quantifying energy flux in regular and irregular sea states, alongside mathematical models for resource estimation across varying environmental conditions. The final section provides illuminating case studies from diverse geographical contexts that demonstrate practical application of assessment methodologies, illustrating the complete process from data acquisition through resource characterization to energy yield prediction while addressing real-world challenges in measurement accuracy, long-term variability, and climate change impacts on resource projections.