Tracers provide a window into the emergent dynamics of fluid systems, and have been applied to study mixing and circulation across planetary scales from the deep interior to the overlying oceans and atmospheres. This two-week summer school will study tracer mixing on Earth, across the Solar System, and on exoplanets. Topics will include Earth’s interior dynamics, geophysical fluid dynamics, physical oceanography, and atmospheric circulation, along with fluid mixing in Solar System objects from Venus to the gas and ice giant planets along with their icy moons, and the broad range of hot, warm, and temperate exoplanets that have or will be characterized by astronomical observations. The school will consist of lectures given by internationally recognized experts in planetary fluid dynamics, presentations by student attendees, and collaborative research projects to forge new implementations and applications of tracers to the study of planetary fluid simulations, experiments, and observations.