Previous literature highlights the crucial role of economic inequality in triggering a range of negative societal outcomes. However, the relationship between economic inequality and the proliferation of conspiracy beliefs remains unexplored. Here, we explore the endorsement of conspiracy beliefs as an outcome of objective country-level (Study 1a, 1b, 1c), perceived (Study 2), and manipulated economic inequality (Studies 3a, 3b, 4a, 4b). In the correlational studies, both objective and perceived economic inequality were associated with greater conspiracy beliefs. In the experiments, participants in the high (compared to the low) inequality condition were more likely to endorse conspiratorial narratives. This effect was fully mediated by anomie (Studies 3a, 3b) suggesting that inequality enhances the perception that society is breaking down (anomie), which in turn increases conspiratorial thinking, possibly in an attempt to regain some sense of order and control. Furthermore, the link between economic inequality and conspiracy beliefs was stronger when participants endorsed a conspiracy worldview (Studies 4a, 4b). Moreover, conspiracy beliefs mediated the effect of the economic inequality manipulation on willingness to engage in collective action aimed at addressing economic inequality. The results show that economic inequality and conspiracy beliefs go hand in hand: economic inequality can cause conspiratorial thinking and conspiracy beliefs can motivate collective action against economic inequality.