School systems--and the challenges they face--are often complex and diverse. Effectively addressing these challenges may require a leadership approach that moves beyond traditional teacher and administrator roles. Teacher leadership is one strategy many states and districts are pursuing to facilitate meaningful change and support better outcomes for their students. To support these efforts, the Teacher Leadership Toolkit 2.0 includes a synthesis of research on teacher leadership, current examples, and useful tools for designing, implementing, and supporting teacher leadership initiatives. Toolkit 2.0 includes 10 supporting resources exploring key aspects of teacher leadership initiatives at the national, state, and local levels. States and districts can use the toolkit to drive planning and decision-making and to build knowledge with stakeholders and colleagues. This toolkit (version 2.0) was developed collaboratively between the Center on Great Teachers and Leaders and Leading Educators to capture key insights from recent teacher leadership initiatives and to provide states and districts with relevant guidance to support effective teacher leadership design models. The original toolkit was developed with significant input from state teams from Iowa, Massachusetts, and Tennessee. This toolkit expands on that original group, including insights from Arkansas, the Department of Defense Education Agency, Hawaii, Iowa, Ohio, Maryland, Michigan, Missouri, Mississippi, Nevada, Rhode Island, South Dakota, and Wisconsin.