There is ample evidence that beauty plays a role in hiring, which is often seen as a form of discrimination or ‘lookism’. Different disciplines have conceptualized and examined this beauty discrimination in multiple ways. Against this background, we review in this handbook chapter several mechanisms that have been theorized to explain this discrimination, such as productivity differences, statistical discrimination, status perceptions, stereotypes, the what's-beautiful-is-good effect, and models of preference-based discrimination. We briefly present empirical studies to substantiate each mechanism, summarize key findings, highlight convergence between mechanisms, and discuss inconsistencies across empirical findings. In our overview, we focus specifically on gender differences in the effects of physical attractiveness and their potential explanations. The chapter closes with a discussion of potential avenues for future research, including variations across occupational contexts, intersections of physical attractiveness with other ascribed characteristics, and new technical ways to vary physical attractiveness and analyze their effects.