An annulment is a lawsuit to have a court declare a marriage was invalid and the parties were never in fact married.

The grounds for an annulment vary from state to state but typically include: (1) the person seeking the annulment (the petitioner) was under age (18 years, for example) and did not have parental consent or a court order; (2) the person seeking the annulment (the petitioner) was under the influence of drugs or alcohol and did not have the capacity to consent to the marriage; (3) either party, for physical or mental reasons, was permanently impotent at the time of the marriage and the other party was not aware of the impotency; (4) the other party used fraud, duress, or force to induce the petitioner to enter into the marriage; (5) at the time of the marriage the petitioner did not have the mental capacity to consent to marriage or to understand the nature of the marriage ceremony because of a mental disease or defect; (6) the other party was divorced from a third party within the 30-day period preceding the date of the marriage ceremony, and at the time of the marriage ceremony the petitioner did not know, and a reasonably prudent person would not have known, of the divorce; and (7) the marriage ceremony took place before any waiting period (72 hours, for example) following issuance of the marriage license.

An annulment on any ground is often available only if the parties did not live together (cohabit) after the party seeking the annulment was no longer under the influence of drugs or alcohol, or learned of the facts that are the basis for the annulment sought. A marriage subject to annulment is often said to be a nullity, void, or void ab initio (void from the beginning).

The grounds for an annulment are usually found in a state’s statutes—often in the family code.

In Alabama, an annulment is a legal procedure that declares a marriage null and void as if it never occurred. Grounds for annulment in Alabama include: lack of capacity to consent due to age (without parental consent or a court order if under 18), incapacity due to intoxication, permanent impotence unknown to the other party, fraud, duress, or force to obtain marriage consent, lack of mental capacity due to mental disease or defect, one party being recently divorced and the other party being unaware, and non-compliance with any statutory waiting period after the marriage license is issued. It is important to note that cohabitation after the discovery of the grounds for annulment may invalidate the claim. These grounds are typically codified in the state's family code or similar statutes. Individuals seeking an annulment should consult with an attorney to understand their rights and the legal process involved.