Social Movements and Collective Behaviour constitutes a dynamic and significant sociological domain that studies organised and unorganised collective actions by groups of people. Collective behaviour typically refers to spontaneous, unstructured activities (like crowds, riots, fads, or panics) that emerge in response to common stimuli, often outside established social norms. Social movements, on the other hand, are more organised, sustained, and goal-oriented collective efforts to bring about or resist social change, often operating outside conventional political institutions. This field examines the emergence, mobilisation (e.g., resource mobilisation theory), strategies, tactics, and impacts of various collective actions, from grassroots activism and protests (e.g., Black Power, Luddite) to broad social and cultural shifts. It analyses how individuals come together to express shared grievances, form collective identities, challenge existing power structures, and ultimately influence the direction of social change.