This Article argues that growing private efforts to address climate change collectively take on the attributes and functions of a governance system that could be vital to societal decarbonization. Instead of evaluating specific initiatives or actions of particular businesses, it explores the entire field of private climate action and offers new ways of thinking about the path ahead. The author explores the opportunities and benefits of private climate governance, tests the current landscape of initiatives against criteria of effectiveness and legitimacy, and suggests a research and action agenda for the climate community to bridge gaps in the system.