This article begins the task of assessing polygamy as a moral ideal. The structure of traditional polygamy, in which only one central spouse may marry multiple partners, necessarily yields two inequalities. The central spouse has greater rights and expectations within each marriage and greater control over the wider family. However, two alternative structures for polygamy can remove these inequalities. In polyfidelity, each spouse marries every other spouse in the family. In “molecular” polygamy, any spouses may marry a new spouse outside (...) the family. These new models of polygamy face additional difficulties, but they can be egalitarian in principle. (shrink)