Bigamy is the act of marrying one person while being legally married to another. Polygamy is the practice or custom (often religious) of having more than one wife or husband at a time. Most states prohibit a party from having more than one marriage license at a time, and in most states bigamy is a crime.
In Montana, as in most states, bigamy is illegal. Under Montana Code Annotated 2021, Section 45-5-611, a person commits the offense of bigamy if they knowingly contract or purport to contract a marriage with another person while legally married to a spouse. Bigamy in Montana is considered a felony offense. Polygamy, which involves having more than one wife or husband at the same time, is also not legally recognized in Montana, and engaging in polygamous marriage can be subject to the same legal penalties as bigamy. Individuals are not permitted to have more than one valid marriage license at a time in Montana, and any attempt to obtain a marriage license while already married may result in criminal charges.