Introduction: As demand for healthcare continues to grow, public health systems are increasingly required to drive efficiency improvement (EI) to address public service funding challenges. Despite this requirement, evidence of EI strategies that have been successful applied at the whole-of-system level is limited. This study reports the development, implementation and evaluation of a novel taxonomy of EI strategies used in public health systems to inform systemwide EI models. Materials and methods: The public health system in New South Wales, Australia, operates a centralised EI model statewide and was the setting for this study. An audit of EI strategies implemented in the NSW Health system between July 2016 and June 2019 was used to identify all available EI strategies within the study timeframe. A content management approach was applied to audit the strategies, with each strategy coded to an EI focus area. Codes were clustered according to similarity, and category names were assigned to each cluster to form a preliminary taxonomy. Each category was defined and examples were provided. The resulting taxonomy was distributed and evaluated by user feedback survey and pre–post study to assess the impact on EI strategy distribution. Results: A total of 1127 EI strategies were identified and coded into 263 unique strategies, which were clustered into nine categories to form the taxonomy of EI strategies. Categories included the following: non-clinical contracts and supplies; avoided and preventable activity; clinical service delivery and patient outcomes; finance and operations; recruitment, vacancies and FTE; staffing models; leave management; staff engagement and development; premium staffing; and clinical contracts and supplies. Evaluative findings revealed a perceived reduction in the duplication of EI work, improved access to EI knowledge and improved engagement with EI processes when using the taxonomy. The taxonomy was also associated with wider use of EI strategies. Conclusions: Whole-of-system EI is an increasing requirement. Using a taxonomy to guide systemwide practice appears to be advanta-geous in reducing duplication and guiding practice, with implications for use in health systems internationally.