Breaking with many established assumptions about how innovation ought to work, open source software projects offer eye-opening examples of novel innovation practices for students and practitioners in many fields. In this article we briefly review existing research on the open source phenomenon and discuss the utility of open source software research findings for many other fields. We categorize the research into three areas: motivations of open source software contributors; governance, organization, and the process of innovation in open source software projects; and competitive dynamics enforced by open source software. We introduce the articles in this special issue of Management Science on open source software, and show how each contributes insights to one or more of these areas.