This chapter, authored by Hayagreeva Rao, Calvin Morrill, and Mayer N. Zald, explores how social movements and collective action contribute to the creation of new organizational forms. It argues that social movements are significant sources of cultural innovation and identifies the conditions under which they can create new organizational forms. The authors emphasize the role of institutional entrepreneurship in this process, expanding the theoretical reach of neo-institutionalism. The introduction highlights the importance of collective action and contention in the construction of new organizational forms, which have been underexplored in organizational ecology and neo-institutionalism. The chapter provides a working definition of organizational form and discusses the relationship between new forms and legitimacy. It also examines four types of organizational and market failures that can lead to social movements, such as trade association failures, inadequate incentives, market mechanisms failing to reduce social costs, and exclusion from conventional channels. The chapter further discusses how social movements thrive under certain conditions, such as when collective action fails due to influence costs, when 'normal' incentives are inadequate for creating public goods, and when market mechanisms are insufficient to address negative externalities. It also explores the role of organizational fields in mediating between organizations and institutions, and how social movements can emerge at the interstices of multiple fields. The authors provide case studies, including the establishment of consumer leagues, the development of alternative dispute resolution (ADR), and the rise of health maintenance organizations, to illustrate how social movements create new organizational forms. They conclude by suggesting directions for further research that link politics, social movements, and organizational change at both macro and micro levels.This chapter, authored by Hayagreeva Rao, Calvin Morrill, and Mayer N. Zald, explores how social movements and collective action contribute to the creation of new organizational forms. It argues that social movements are significant sources of cultural innovation and identifies the conditions under which they can create new organizational forms. The authors emphasize the role of institutional entrepreneurship in this process, expanding the theoretical reach of neo-institutionalism. The introduction highlights the importance of collective action and contention in the construction of new organizational forms, which have been underexplored in organizational ecology and neo-institutionalism. The chapter provides a working definition of organizational form and discusses the relationship between new forms and legitimacy. It also examines four types of organizational and market failures that can lead to social movements, such as trade association failures, inadequate incentives, market mechanisms failing to reduce social costs, and exclusion from conventional channels. The chapter further discusses how social movements thrive under certain conditions, such as when collective action fails due to influence costs, when 'normal' incentives are inadequate for creating public goods, and when market mechanisms are insufficient to address negative externalities. It also explores the role of organizational fields in mediating between organizations and institutions, and how social movements can emerge at the interstices of multiple fields. The authors provide case studies, including the establishment of consumer leagues, the development of alternative dispute resolution (ADR), and the rise of health maintenance organizations, to illustrate how social movements create new organizational forms. They conclude by suggesting directions for further research that link politics, social movements, and organizational change at both macro and micro levels.