Political revolutions, economic meltdowns, mass ideological conversions and collective innovation adoptions occur often, but when they do happen, they tend to be the least expected. Based on the paradigm of 'leading from the periphery', this groundbreaking analysis offers an explanation for such spontaneity and apparent lack of leadership in contentious collective action. Contrary to existing theories, the author argues that network effects in collective action originating from marginal leaders can benefit from a total lack of communication. Such network effects persist in isolated islands of contention instead of overarching action cascades, and are shown to escalate in globally dispersed, but locally concentrated networks of contention. This is a trait that can empower marginal leaders and set forth social dynamics distinct from those originating in the limelight. Leading from the Periphery and Network Collective Action provides evidence from two Middle Eastern uprisings, as well as behavioral experiments of collective risk-taking in social networks.