This evaluation study, performed in line with the Better Regulation Guidelines, serves as an input into the ex-post evaluation of Horizon 2020, the EU framework programme for Research and Innovation 2014-2020. Horizon 2020 was adopted in the context of the Europe 2020 Strategy, and was designed to drive economic growth and create jobs by coupling research and innovation (R&I), with an emphasis on excellent science, industrial leadership and tackling societal challenges. This study assesses the overall contribution of Horizon 2020 to excellent science across the framework programme with a particular focus on the activities under Pillar 1, Excellent Science (i.e. the European Research Council (ERC), Marie Skłodowska-Curie Actions (MSCA), European research infrastructures (INFRA), and Future and Emerging Technologies (FET)), as well as the horizontal pillars Spreading Excellence and Widening Participation (SEWP) and Science with and for Society (SwafS). The study builds on the Horizon 2020 intervention logic and relies on a wide range of methods. These include (but are not limited to) desk research, a broad-scope interview programme, 15 case studies and four international benchmark studies, a survey programme, a bibliometric analysis, econometric modelling, and the analysis of (unstructured and EC monitoring) data. The findings of the study respond to a set of evaluation questions covering the five evaluation criteria: relevance, coherence, efficiency, effectiveness and EU added value. This study places a stronger focus on the key findings, conclusions and recommendations in relation to efficiency, effectiveness and EU added value, as the other evaluation criteria are analysed in greater depth by other ongoing studies.