Social movements are familiar features of the socio-political landscape, yet they can be hard to define. Broadly speaking, social movements are composed of multiple collective actions. Collective action involves people doing something together repeatedly or over a sustained period of time to achieve a shared purpose. People’s engagement with authority and/or powerful actors often takes place through spontaneous collective action outside established institutional channels. Collective action is increasingly being recognised as a pathway for: enhanced agency and voice for those who may not wish to use formal representation and who face social exclusion; broader participation in decision-making; and more transparent, responsive and accountable national governments and international governance institutions. Social movements emerge when enough people feel alienated or excluded from the world around them or develop a deep distrust of how political institutions manage society. They express social, cultural, political or economic concerns locally, nationally or transnationally, and they are found in both democratic and repressive states. Information and communication technologies (ICTs) such as the internet, mobile phones and social media platforms have opened new spaces of engagement for collective action.