Because individuals' fundamental right to water is often taken for granted, little is known about why individuals participate in water activism. We examine how individuals identify with and intend to participate in the Italian Water Movement to defend the “public management” of water supply. Building on the collective-action literature, we test an explanatory model in which the perceived violation of the right to water and group and participative-efficacy beliefs increase movement identification, which predicts subsequent activism. Study 1 (N = 153 activists) largely confirmed our hypotheses: right violation and participative efficacy uniquely influenced movement identification, which in turn predicted activism. Study 2 corroborated these findings by employing a broader sample of 132 Italian citizens, with right violation, participative and group-efficacy beliefs predicting movement identification, which in turn predicted activism. We discuss the theoretical and practical implications of these findings.