The 2002 Fusion Summer Study was conducted July 8–19, 2002, in Snowmass, CO, and carried out a critical assessment of major next steps in the fusion energy sciences program in both magnetic fusion energy (MFE) and inertial fusion energy (IFE). The conclusions of this study were based on analysis led by over 60 conveners working with hundreds of members of the fusion energy sciences community extending over eight months. This effort culminated in two weeks of intense discussion by over 250 U.S. and 30 foreign fusion physicists and engineers present at the 2002 Fusion Summer Study. This is the Executive Summary of the study report. Details are posted at http://web.gat.com/snowmass