The Impact Investor is a project to build data-driven and practitioner-guided knowledge for the rapidly growing field of impact investing. It is a partnership between InSight, the Center for the Advancement of Social Entrepreneurship at Duke University, and ImpactAssets. It is supported by the Omidyar Network, the Annie E.Casey Foundation, the RS Group (Hong Kong), the F.B. Heron Foundation, and Deutsche Bank. This first report provides an overview of the project and outlines the growth and development of impact investing, ongoing challenges within the space, and the need for evidence and engagement.