The USAID-funded Systems for Improved Access to Pharmaceuticals and Services (SIAPS) Program and its predecessor programs have assisted numerous countries in strengthening governance to promote robust decision making, enhance accountability, reduce opportunities for corruption, and improve efficiencies to enable better access to and use of quality-assured medicines. This compendium draws on these experiences and provides a collection of examples of strategies and approaches for strengthening governance in pharmaceutical systems. The compendium highlights accumulated insights into factors that may have enabled or constrained the success of governance improvement initiatives. The intention is to systematically bolster knowledge, in alignment with USAID’s collaborating, learning, and adapting approach, so that stakeholders may examine the applicability of lessons learned and apply them in different settings to maximize resources and attain better development results. The compendium begins by defining governance, then explains its importance in pharmaceutical systems and introduces the framework SIAPS has used to guide its governance strengthening activities. It presents eight case studies on SIAPS’ work in enhancing governance in pharmaceutical systems, summarizes challenges commonly encountered and lessons learned, and closes with some reflections on the usefulness of SIAPS’ governance-strengthening framework.