Polygamy is the practice of having more than one spouse at the same time. Polygamy as a crime originated in the common law, and it is now outlawed in every state. In the United States, polygamy was declared unlawful through the passing of Edmunds Anti-Polygamy Act of 1882.
In Murphy v. Ramsey, 114 U.S. 15, the Supreme Court held that polygamist means “every person who has a husband or wife living, who, in a territory or other place over which the United States have exclusive jurisdiction, hereafter marries another, whether married or single, and any man who hereafter simultaneously or on the same day marries more than one woman, in a territory or other place over which the United States have exclusive jurisdiction.”
As a crime, polygamy is often synonymous with bigamy (marrying one spouse while already being married to another).
[Last updated in March of 2022 by the Wex Definitions Team]