Concubines are not legal in the United States in the sense that no state or federal law recognizes concubinage as a relationship. There is no “concubine” status in any statute, no rights that flow from the label, and no court that will treat it as anything other than two adults living together. That said, the underlying arrangement — an unmarried couple sharing a home and a life — is lawful almost everywhere. It just comes with far fewer protections than most people assume.
What “Concubine” Means Under U.S. Law
Nothing. You will not find the word “concubine,” “concubinage,” or any equivalent defined in any federal statute or state code. The term historically described a woman who lived with a man in a marriage-like arrangement without a wife’s legal standing. In modern American law, that description simply matches unmarried cohabitation. Using the older word does not create rights, does not create obligations, and does not change how a court will treat the relationship if it ends or if one partner dies.
Marriage, by contrast, is a legal contract that triggers specific rights: inheritance protections, joint tax filing, spousal support on divorce, Social Security survivor benefits, and the ability to sponsor a partner for immigration. No parallel framework exists for anything short of marriage. Calling a partner a concubine, a companion, or a life partner produces the same legal result, which is none.
Is Living Together Outside Marriage Legal?
Yes, in nearly every state. Statutes that once criminalized unmarried cohabitation have been repealed across the country over the past several decades. Mississippi is the only state that still has a cohabitation statute on the books, and prosecutions under it are essentially nonexistent.
A few criminal laws can still intersect with these arrangements, though, and they are worth knowing about.
Bigamy
If either partner is already legally married to someone else, going through a second marriage ceremony or obtaining a second marriage license is bigamy in every state. Penalties range from misdemeanors to felonies depending on the jurisdiction. Simply cohabiting with a new partner while still married to someone else is not bigamy on its own; the crime requires the second marriage itself.
Prostitution
An unmarried couple where one partner supports the other financially is not engaged in prostitution. If the arrangement is structured as a direct exchange of money for sexual acts, however, prostitution laws apply. Prostitution is illegal in 49 states. Nevada is the sole exception, and only in licensed brothels in counties with populations under 700,000, which excludes Las Vegas and Reno.1Nevada Legislature. Nevada Revised Statutes 201-354 – Unlawful for Customer to Engage in Prostitution or Solicitation Except in Licensed House of Prostitution This matters for cohabitation agreements too: courts refuse to enforce a contract between partners if the financial terms are tied to sexual services.
Adultery
A shrinking number of states still have adultery statutes on the books, but prosecutions are vanishingly rare. Minnesota repealed its adultery law in 2023. Where these statutes still exist, they can occasionally surface as evidence of fault in a divorce, but they are almost never used against cohabiting couples directly.
What You Give Up Without Marriage
Legal is not the same as protected. Unmarried partners are treated as legal strangers in most contexts, and the gaps are wider than people expect.
Inheritance
Every state’s intestacy laws send a deceased person’s assets to spouses, children, parents, and siblings, in that order. An unmarried partner is not on the list. If your partner dies without a will, their property passes to blood relatives. You could share a home for thirty years, raise children together, and pay the mortgage together, and still have no legal claim to the house if only your partner’s name is on the deed. A will or trust naming you as a beneficiary is the only reliable fix.
Social Security Survivor Benefits
A surviving spouse can collect Social Security benefits based on the deceased worker’s earnings record. An unmarried partner cannot, regardless of how long the relationship lasted or how financially dependent one partner was on the other.2Social Security Administration. Who Is Eligible to Receive Social Security Survivors Benefits and How Do I Apply Even an ex-spouse who was married for at least 10 years and did not remarry before age 60 can qualify. A partner of 20 years who never married gets nothing.
Medical Decisions
Federal regulations require hospitals accepting Medicare or Medicaid to let patients designate their own visitors, so visitation is generally not the problem it once was. Decision-making authority is. If your partner is incapacitated and has not signed a healthcare power of attorney naming you, providers will turn to legal next of kin, usually a parent, adult child, or sibling. You can be shut out of medical decisions entirely, even when you know your partner’s wishes better than anyone.
Taxes and Shared Money
Unmarried couples cannot file a joint federal return no matter how long they have lived together or how intertwined their finances are. Each partner files as single or, with a qualifying dependent, as head of household.3Internal Revenue Service. Filing Status Married couples can also transfer unlimited property to each other without triggering gift or estate taxes. Unmarried partners cannot.
Individual debts stay individual — moving in together does not make you responsible for your partner’s student loans or credit cards. But that protection erodes the moment you combine finances. Joint accounts, co-signed loans, and jointly financed purchases create shared liability that survives the relationship. If you split up, the bank does not care who was at fault.
Common Law Marriage Is the Narrow Exception
People sometimes assume that living together long enough turns into a marriage automatically. It does not. No state creates a marriage based on time alone. Common law marriage, where it still exists, requires that both partners genuinely intend to be married, hold themselves out to the community as married, and live together while doing so.
Only a handful of jurisdictions still allow new common law marriages: Colorado, Iowa, Kansas, Montana, Rhode Island, South Carolina, Texas, Utah, and the District of Columbia, each with its own requirements.4National Conference of State Legislatures. Common Law Marriage by State Colorado and Kansas require both parties to be at least 18. Texas lets couples either meet the traditional elements or file a Declaration of Informal Marriage with the county clerk. New Hampshire recognizes common law marriage only for inheritance. Georgia, Ohio, Oklahoma, and Pennsylvania recognize common law marriages formed before a cutoff date but no longer allow new ones.
If you meet the requirements in a state that recognizes common law marriage, you have the same legal rights as any married couple. If you don’t, or you live somewhere that doesn’t recognize it, you are legally single no matter how long you have been together.
How to Protect Yourself Without Getting Married
Couples who want to stay unmarried can close most of the practical gaps with a few documents.
A cohabitation agreement is a written contract between unmarried partners covering who owns what, how expenses are shared, and what happens to property if the relationship ends. It functions like a prenup for people who are not getting married. Courts in most states enforce these agreements as long as both partners sign voluntarily, the terms are in writing, and the contract does not tie support to sexual services. Legal fees for drafting one typically run between $500 and $800.
Even without a written contract, courts in some states will look at how a couple actually behaved to determine whether an implied agreement existed, a doctrine that opened the door to so-called palimony claims. Proving an implied contract is much harder than enforcing a written one, and several courts have refused to recognize oral agreements for lack of evidence. Put it in writing.
Alongside the cohabitation agreement, unmarried partners who share a life should have:
- A will or trust naming the partner as a beneficiary, since intestacy laws will not.
- A durable power of attorney for healthcare, giving the partner authority to make medical decisions.
- A durable power of attorney for finances, allowing the partner to manage bills and accounts if needed.
These documents are inexpensive compared to the problems they prevent.
Immigration: No Path for an Unmarried Partner
Federal immigration law recognizes marriage and nothing less. To sponsor a partner for a green card, you must be legally married, and USCIS will recognize the marriage only if it was legally valid where performed, entered into in good faith, and both parties were free to marry.5U.S. Citizenship and Immigration Services. Policy Manual – Chapter 6 Spouses Common law marriages count if they are valid in the state where they were established. An informal long-term relationship does not, however committed.
For couples not yet married, the K-1 fiancé visa lets a U.S. citizen bring a foreign partner into the country, but the couple must marry within 90 days of the partner’s arrival or the foreign partner loses status and must leave.6U.S. Citizenship and Immigration Services. Visas for Fiancees of US Citizens Both partners must be legally free to marry, meaning any prior marriages have to be ended by divorce, death, or annulment. There is no visa category for a concubine or a long-term unmarried partner.