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 Connecticut, common law marriages are not recognized. This means that couples cannot become legally married in Connecticut simply by living together for a certain period of time or by holding themselves out to others as a married couple. Instead, to be legally recognized as married in Connecticut, a couple must obtain a marriage license and have a formal wedding ceremony. While Connecticut does not establish new common law marriages, it may recognize a common law marriage that was validly formed in another state where such marriages are recognized, under the full faith and credit clause of the U.S. Constitution. This recognition would be subject to the specific laws and judicial decisions of Connecticut regarding the treatment of out-of-state common law marriages.