Common law marriage—also known as marriage without formalities or informal marriage—is marriage without a wedding or marriage ceremony and without a marriage license. Some states recognize common law marriage under certain circumstances—such as when the parties agree to be married, live together (cohabit) after agreeing to be married, and represent to others that they are married (holding themselves out as a married couple).

Other states previously recognized common law marriages, but no longer recognize such marriages after a certain date on which the law was changed—usually by statute. In other states, common law marriage has not been recognized by the legislature in a statute, but the courts have recognized common law marriage in court opinions or case law.

In Oklahoma, common law marriage is recognized by the state. To establish a common law marriage in Oklahoma, couples must meet certain criteria: they must have the capacity to marry, mutually agree to be married, cohabit, and hold themselves out to the public as married. This means that the couple must present themselves as a married couple in social situations and typically should have some form of proof of their mutual agreement to be married, such as joint financial accounts, joint ownership of property, or the use of the same last name. It is important to note that once a common law marriage is established in Oklahoma, it is legally binding and has the same legal effects as a ceremonial marriage. To dissolve a common law marriage, the couple must go through the formal divorce process. Additionally, if a couple has a common law marriage in Oklahoma and moves to a state that does not recognize common law marriage, their marriage may still be considered valid if it was established under Oklahoma law.