This paper provides an account of the developmental origins of our belief in free will based on research from a range of ages—infants, preschoolers, older children, and adults—and across cultures. The foundations of free will beliefs are in infants' understanding of intentional action—their ability to use context to infer when agents are free to “do otherwise” and when they are constrained. In early childhood, new knowledge about causes of action leads to new abilities to imagine constraints on action. Moreover, unlike (...) adults, young children tend to view psychological causes (i.e., desires) and social causes (i.e., following rules or group norms, being kind or fair) of action as constraints on free will. But these beliefs change, and also diverge across cultures, corresponding to differences between Eastern and Western philosophies of mind, self, and action. Finally, new evidence shows developmentally early, culturally dependent links between free will beliefs and behavior, in particular when choice‐making requires self‐control. (shrink)