People mobilisation is a common tool used to challenge state authority. In the United States (U.S.), since 2013, people have joined Black Lives Matter marches in different states to challenge police brutality. More than 1,030 protest actions have been held in the name of Black Lives Matter. Following Jesse Williams’ speech at the 2016 BET awards, and the recent death of Philando Castile and Alton Sterling, Black Lives Matter has taken centre stage again, reviving the conversation on mainstream and social media. This paper unpacks Black Lives Matter as a social movement by tracing back the definitions of people’s mobilisation and social movements.