Love is prototypically organized such that some features of love are clearer, better examples of the concept than others, but little work has been done to explain how laypeople’s love prototypes translate into cognition and emotion in actual romantic relationships. To help fill this gap, this dissertation examined the role of love prototypes as a source of positive illusions in perceiving romantic partners, as well as the implications of these perceptions for relationships. More specifically, it was predicted that though people would be somewhat accurate in their perceptions of their partner’s traits, feelings, and behaviors, people would also perceive their partner as possessing the traits, feelings, and behaviors that are consistent with the features most central to their idea of love. In turn, it was expected that when people perceive their romantic partner consistently with their central love prototypes, they would feel more loved and satisfied in their relationship. A three-wave longitudinal study tested these predictions. It was consistently found that people’s individualized love prototypes predicted their perceptions of their partner, suggesting that love prototypes are indeed a source of positive illusions in relationships. Perceptions of partner’s traits, feelings, and behaviors were also predicted by partner’s actual traits, feelings, and behaviors, thus demonstrating that people are both accurate and biased in their perceptions of their partner. Further, the association between perceivers’ love prototype centrality and their perceptions of their partner was especially strong when they had a strong desire to be loved by their partner, and was weaker when perceivers were higher in avoidant attachment, ambivalent attachment, rejection sensitivity, and, counter to predictions, when the feature being perceived was more ambiguous. Mixed support was found for the role of self-esteem and relational-interdependent self-construal as moderators of the relationship between perceivers’ love prototype centrality and their partner perceptions. Importantly, the more people perceived their partner as consistent with their love prototypes, the more loved and satisfied they felt in their relationship, though this greater felt love was limited to a particular context. Overall, these findings demonstrate that illusory perceptions that one’s partner aligns with one’s love prototypes are beneficial for perceivers.