The notion of equality attracts both proponents and critics of nonmonogamy. Inequality is a widely discussed objection to nonmonogamy. Simultaneously, equality is highlighted as a core value in ethical nonmonogamy. The notions of equality and inequality in these debates have not been clearly conceptualized. In order to propose a conception of egalitarian nonmonogamy, it is important to first understand possible inequalities within it. This paper establishes a clearer and in-depth understanding of inequalities in nonmonogamy by categorizing inequalities in traditional polygamy (...) into different kinds. I argue that these inequalities are generally unjust. Although these inequalities are common in traditional polygamy, the objection that polygamy—as a type of marriage—is inherently unequal and unjust is not a convincing argument. By contrast, not all kinds of equality—such as equal love or equal number of partners—are morally significant. I conclude this paper by providing some groundwork for future research on egalitarian nonmonogamy. (shrink)