In the context of recent debates about same-sex marriage, consensually nonmonogamous (CNM) relationships have recently begun making their way into media discussions. In the current research, we investigated whether stigma is attached to these nonnormative romantic relationships and, conversely, whether halo effects surround monogamous relationships. In Study 1 we analyzed open-ended responses to the question “what are the benefits of monogamy?”. The most commonly mentioned benefits included the promotion of commitment and health (especially the prevention of sexually transmitted infections [STIs]). In Study 2, descriptions of CNM relationships were strongly stigmatized and a substantial halo effect surrounded monogamous relationships. Specifically, monogamous relationships were rated more positively than CNM relationships on every dimension (both relationship-relevant and arbitrary relationship-irrelevant factors) that we examined and across diverse social groups, including CNM individuals themselves. In Study 3, we conducted a person perception study in which participants provided their impressions of a monogamous or a CNM relationship. The monogamous couple was rated overwhelmingly more favorably than the CNM relationship. Finally, in Study 4, we replicated the findings with a set of traits that were generated with regard to relationships in general (rather than monogamous relationships, specifically) and with a broader set of arbitrary traits. Across all studies, the results consistently demonstrated stigma surrounding CNM and a halo effect surrounding monogamy. Implications for future research examining similarities and differences between monogamous and CNM relationships are discussed.