Common-law marriage, also known as sui iuris (sui juris) marriage, informal marriage, marriage by habit and repute, or marriage in fact is a legal framework in a limited number of jurisdictions where a couple is legally considered married, without that couple having formally registered their relation as a civil or religious marriage. The original concept of a "common-law marriage" is a marriage that is considered valid by both partners, but has not been formally recorded with a state or religious registry, or celebrated in a formal religious service. In effect, the act of the couple representing themselves to others as being married, and organizing their relation as if they were married, acts as the evidence that they are married.
The term common-law marriage has wide informal use, often to denote relations which are not legally recognized as common-law marriages. The term common-law marriage is often used colloquially or by the media to refer to cohabiting couples, regardless of any legal rights that these couples may or may not have, which can create public confusion both in regard to the term and in regard to the legal rights of unmarried partners.
The term "common-law marriage" is often used incorrectly to describe various types of couple relationships, such as cohabitation (whether or not registered), or other legally formalized relations. Although these interpersonal relationships are often called "common-law marriage" they differ from true common law marriage, in that they are not legally recognized as "marriages", but are a parallel interpersonal status, known in most jurisdictions as "domestic partnership", "registered partnership", "conjugal union", "civil union", etc. In Canada, for instance, while couples in "marriage-like relationships" may have many of the rights and responsibilities of a marriage (laws vary by province), couples in such partnerships are not legally considered married, although they may be legally defined as "unmarried spouses" and for many purposes (such as taxes, financial claims, etc.) they are treated as if they were married. In recent years, the term common law marriage has gained increased use as a generic term for all unmarried couples – however, this term has a narrow legal meaning. First of all, one can only talk of "common law marriage" if such marriage was formed in a jurisdiction which actually applies the common law. A 2008 poll in the UK showed that 51% of respondents incorrectly believed that cohabitants had the same rights as married couples.