In response to the need to develop leaders to guide the implementation of the Next Generation Science Standards (NGSS), the Carnegie Corporation of New York provided funding to WestEd to develop a framework that defines the leadership knowledge and actions needed to effectively implement the NGSS. The development of the framework entailed completing a review of the literature to identify the leadership knowledge and actions necessary for implementing new standards; convening an NGSS Leadership Summit with 21 national science education experts who have been implementing the NGSS in states and districts; and conducting 23 interviews with leaders at all levels of the system in California and Washington to gather voices from the field (many of which are included in quotations throughout this framework document). The "Framework for Leading Next Generation Science Standards Implementation" is a synthesis of information gathered from all of these activities. This new framework provides insight into the full array of what leaders need to know--and be able to do--to lead NGSS implementation, from inspiration and vision to data use and quality professional learning. Developed by science education experts and project staff, the framework is designed to provide a comprehensive vision of the leadership knowledge and the critical actions that need to be taken to plan for and implement the NGSS. It is intended to inform the work of all leaders at all levels of the system--from teacher leaders to district leaders to state education leaders--who are charged with supporting and implementing the NGSS. The framework can be used as a self-assess­ment for leaders to identify areas for their further development to prepare them to lead standards implementation, and as a planning guide to help leaders think through the critical actions that they need to take in order to lead and support others for NGSS implementation.