The difference between bigamy and polygamy comes down to scope and legal formality: bigamy is marrying a second person while you are still legally married to the first, and polygamy is the broader practice of living with more than one spouse at the same time. Bigamy is a specific legal act tied to a marriage license. Polygamy describes an ongoing arrangement that may or may not involve any licenses at all. Both are illegal everywhere in the United States, but they trigger the law in different ways.
What Counts as Bigamy
Bigamy happens when someone goes through a marriage ceremony or obtains a marriage license with a new partner before legally ending an existing marriage through divorce or annulment. The defining element is the second legal marriage. Separation does not count. Even years apart from a first spouse leaves you legally married until a court finalizes the divorce, and marrying again before that point is bigamy.
The second marriage is typically void, meaning it has no legal effect from the start. In narrower circumstances, such as when someone genuinely believed a prior spouse had died, the second marriage may instead be voidable, requiring a court to formally annul it rather than being automatically invalid.
Deception is often part of the picture. The new partner frequently has no idea the other person is already married. That innocent partner ends up in a relationship the state does not recognize, with no automatic claim to marital property and the fallout of discovering the marriage was built on a lie.
What Counts as Polygamy
Polygamy is the practice of having more than one spouse simultaneously. Polygyny is one husband with multiple wives; polyandry is one wife with multiple husbands. Polygyny is far more common, historically and today.
Unlike bigamy, polygamy usually involves the knowledge and participation of everyone in the household. It is often rooted in religious tradition or cultural custom rather than deception. Many polygamous families in the U.S. do not seek multiple marriage licenses. They may have one legal marriage and treat additional partners as “spiritually” married without involving the state. The relationships function as marriages socially but do not always trigger the legal paperwork that bigamy charges rely on.
The Core Differences
Three things separate the two: the number of relationships, the paperwork involved, and the role of deception.
Bigamy involves exactly two marriages. Polygamy can involve any number beyond one. Bigamy requires an actual second legal marriage, with a license and a ceremony recognized by the state. Polygamy may exist entirely outside the formal legal system.
Intent and knowledge split them further. Bigamy typically hides the first marriage from the new spouse. Polygamy is generally open among the partners involved. The overlap that confuses people is this: if someone practicing polygamy obtains multiple marriage licenses, they have committed bigamy as well. The polygamy is the lifestyle. The bigamy is the specific legal violation of holding two valid marriage certificates at once.
Criminal Penalties for Each
Bigamy is a crime in all 50 states, the District of Columbia, and U.S. territories. The severity varies widely. Most states classify it as a felony or serious misdemeanor, with prison sentences typically ranging from 30 days to five years, and reaching up to 10 years in the most serious jurisdictions. Fines can exceed $25,000. One state recently reduced basic bigamy to a minor infraction while reserving felony charges for cases involving fraud, coercion, or connected criminal conduct.
Polygamy is also criminalized throughout the United States. Every state has a prohibition, and the Supreme Court upheld the constitutionality of these laws in Reynolds v. United States, ruling that religious belief in the correctness of polygamy does not exempt someone from criminal prosecution.1Justia. Reynolds v. United States The Court drew a clear line: the government cannot regulate what you believe, but it can regulate what you do.
In practice, polygamy prosecutions are rare. Federal authorities largely defer to state law, and most states only pursue charges when polygamy is connected to other offenses like fraud, abuse, or welfare violations. A person quietly living in a plural household without multiple marriage licenses is unlikely to face prosecution, though the conduct remains technically illegal.
Why Innocent Second Spouses Still Get Hurt
A bigamous marriage is typically void from inception. It never had legal force. The second spouse has no automatic right to property division, spousal support, or inheritance under marriage law. Joint accounts, beneficiary designations, and financial arrangements built on the assumption of a valid marriage can all unravel.
The putative spouse doctrine offers some protection. Recognized in a number of states, this principle grants certain marital rights to someone who entered a marriage in good faith, genuinely believing it was valid. A putative spouse may be entitled to property division and support just as if the marriage were real. Good faith is the key: once you learn the marriage is invalid, your putative spouse status ends and you cannot acquire further rights under it.2Social Security Administration. POMS GN 00305.085 – Putative Marriage
Immigration and Tax Fallout
For non-citizens, the immigration consequences can outweigh the criminal ones. Federal law makes any immigrant coming to the United States to practice polygamy inadmissible, regardless of visa category.3Office of the Law Revision Counsel. 8 USC 1182 – Inadmissible Aliens No waiver is available. The bar requires intent to actually practice polygamy in the U.S.; past practice abroad or a mere belief in it is not enough on its own.4U.S. Department of State. Foreign Affairs Manual – Ineligibility Based on Other Activities A bigamy conviction, by contrast, may be classified as a crime involving moral turpitude, which is a separate ground for visa ineligibility.
Both can also bar a finding of good moral character, which is required for naturalization. An applicant who intentionally committed bigamy, even without a criminal conviction, will generally fail that requirement. The typical remedy is to end the bigamous or polygamous relationship and wait five years before applying. Someone who committed unintentional bigamy, genuinely believing they were free to marry, may be able to resolve the issue by dissolving the invalid marriage without the five-year wait. Polygamy practiced in a foreign country before obtaining a green card generally will not affect a naturalization application; problems arise if it continues after permanent resident status.
Taxes are the other quiet casualty. The IRS determines marital status by whether your marriage is recognized under state law.5Internal Revenue Service. Publication 501 – Dependents, Standard Deduction, and Filing Information A void bigamous marriage was never recognized, so any joint returns filed during that period used the wrong status. The IRS cross-checks Social Security numbers, and two people both claiming the same individual as a spouse can trigger a notice. The agency may reclassify the filing status, resulting in additional tax owed plus penalties and interest. Health insurance coverage, Social Security survivor benefits, pension beneficiary designations, and estate planning documents that reference a “spouse” can all be disrupted in the same way.
Defenses If You’re Charged With Bigamy
Here is where many people get an unpleasant surprise. A significant number of states treat bigamy as a strict liability crime, meaning the prosecution does not have to prove you intended to break the law. If you married while still legally married, the offense is complete, even if you genuinely believed your divorce was final or your first spouse had died.
Some defenses do exist, though they vary by jurisdiction:
- A valid prior divorce. If your first marriage was legally dissolved before the second one, there is no bigamy. The divorce has to be valid in the state where you are charged; a foreign divorce that is not recognized domestically will not protect you.
- A good faith belief your spouse was dead. Several states allow this defense, especially after a statutory waiting period, often five to seven years of absence with no contact. Remarrying before that period expires generally will not qualify.
- Reliance on counsel. In limited circumstances, being affirmatively misled by an attorney about the status of your divorce may provide a defense. It is difficult to prove and not recognized everywhere.
Separation, even long-term legal separation, is never a defense. A separation agreement does not dissolve a marriage. Neither does a belief that your first marriage was void because of some procedural flaw. Until a court enters a divorce decree, you are married, and marrying someone else is bigamy.