 Collective intentionality is the power of minds to be jointly directed at objects, matters of fact, states of affairs, goals, or values. Collective intentionality comes in a variety of modes, including shared intention, joint attention, shared belief, collective acceptance, and collective emotion. Collective intentional attitudes permeate our everyday lives, for instance when two or more agents look after or raise a child, grieve the loss of a loved one, campaign for a political party, or cheer for a sports team. They are relevant for philosophers and social scientists because they play crucial roles in the constitution of the social world. In joint attention, the world is experienced as perceptually available for a plurality of agents. This establishes a basic sense of common ground on which other agents may be encountered as potential cooperators. Shared intention enables the participants to act together intentionally, in a coordinated and cooperative fashion, and to achieve collective goals. The capacity for shared belief provides us with a common stock of knowledge, and thus with a background against which relevant new information which we may want to share with others becomes salient. Collective acceptance is crucial for the development of language, and for a whole world of symbols, institutions, and social status. Collective emotions provide us with a shared conception of what matters to us, together, and they establish readiness for joint action. In virtue of capacity for collective intentionality, we can (and should) engage in joint reasoning and deliberation, and (re-)organize ourselves to make sure that the way we live together is how we, collectively, want it to be, from our small-scale communities to global politics.