Introduction: There are good reasons to study urban innovation from a systemic perspective. A key finding in innovation research is that organizations rarely innovate in isolation, but in interaction with clients, competitors, suppliers, and other organizations. A system perspective is useful in understanding and analyzing these interactions. Cities and urban regions are increasingly recognized as key milieus in which these interactions occur. The urban innovation system approach conceptualizes the city or urban region as a context in which innovations emerge from complex interactions between urban actors—firms, citizens, governments, knowledge institutes— in a particular institutional setting. The systemic view of innovation departs from traditional linear models that depict innovation as a staged process that starts with (basic) scientific research and ends with commercialization by companies. Innovation processes are much more complex and diverse, influenced by multiple actors that interact in networks with feedback loops, and involving many types of knowledge beyond scientific knowledge. Urban innovation systems are nested in innovation systems on other spatial levels—regional, national, international. Studies on urban innovation systems seek to explain how innovations emerge in an urban context, why urban regions differ in their innovative performance, and also address questions on the governance and management of such systems. Studies in this field draw from a variety of disciplines including economic geography, urban and regional economics, political sciences, innovation studies, social sciences, and urban planning.