Despite social and economic advances around the world, poverty and disease persist, exacerbated by the mounting challenges of climate change, natural disasters, political conflict, mass migration, and economic inequality. While governments have committed to addressing these challenges-- with such efforts as the Paris Agreement on Climate Change or the Millennium Development Goals-- our aspirations run deeper than our pockets. Traditional public and philanthropic dollars are not enough. Innovative finance brings governmental, commercial, and philanthropic resources to bear on the common good: meeting the needs of the poor and underserved, solving global problems, and building a more sustainable and inclusive prosperity. Innovative finance has provided polio vaccines to children in the DRC, crop insurance to farmers in India, pay-as-you-go solar electricity to Kenyans, and affordable housing and transportation to New Yorkers. Capital and the Common Good shows how market failure in one context can be solved with market solutions from another: an expert in securitization bundles future development aid into bonds to pay for vaccines today; an entrepreneur turns a mobile phone into an array of financial services for the unbanked; and policy makers adapt pay-for-success models from the world of infrastructure to human services like early childhood education, maternal health, and job training. Surveying the successes and missteps of these efforts, Keohane argues that innovative finance is as much about incentives and sound decision making as it is about money. When it works, innovative finance gives us the tools, motivation, and security to invest in our shared future.