When perceiving, explaining, or criticizing human behavior, people distinguish between intentional and unintentional actions. To do so, they rely on a shared folk concept of intentionality. In contrast to past speculative models, this article provides an empirically-based model of this concept. Study 1 demonstrates that people agree substantially in their judgments of intentionality, suggesting a shared underlying concept. Study 2 reveals that when asked to directly define the term intentional, people mention four components of intentionality: desire, belief, intention, and awareness. (...) Study 3 confirms the importance of a fifth component, namely, skill. In light of these findings, the authors propose a model of the folk concept of intentionality and provide a further test in Study 4. The discussion compares the proposed model to past ones and examines its implications for social perception, attribution, and cognitive development. (shrink)