This article investigates the often cited and dismissed, but rarely examined, relationship between legalizing same-sex marriage and polygamy. Employing a comparative historical analysis of U.S. and South African jurisprudence, ideology, and cultural politics, we examine efforts to expand, restrict, and regulate the gender and number of legally recognized conjugal bonds. South African family jurisprudence grants legal recognition to both same-sex marriage and polygyny, while the United States prohibits and resists both. However, social and material conditions make it easier to practice (...) family diversity in the U.S. than in South Africa. Our analysis of the very different histories of polygamy and same-sex marriage in the two societies suggests the centrality of racial politics to marriage regimes, yielding paradoxical narratives about the implications of legal same-sex marriage for the future of polygamy and sexual democracy. If there is a slippery marital slope, we argue, it does not tilt in a singular or expected direction. (shrink)