The Generic Deep Geologic Disposal Safety Case presents generic information that is of use in understanding potential deep geologic disposal options in the U.S. for used nuclear fuel (UNF) from reactors and high-level radioactive waste (HLW). Potential disposal options include mined disposal in a variety of geologic media (e.g., salt, shale, granite), and deep borehole disposal in basement rock. The Generic Safety Case is intended to be a source of information to provide answers to questions that may arise as the U.S. works to develop strategies to dispose of current and future inventories of UNF and HLW. DOE is examining combinations of generic geologic media and facility designs that could potentially support development of a geologic disposal facility. This document serves as a synthesis of information from generic and other repository disposal system work with a focus on postclosure safety (assumptions, safety strategy, generic natural and engineered systems’ descriptions, qualitative and quantitative assessments, discussion of domestic and international programs, analogs, history, risk information, challenges) and as a planning tool for future R&D; this product may be of use to stakeholders and decision makers with interest in the character and safety of geologic disposal systems.