Legal separation (sometimes judicial separation, separate maintenance, divorce a mensa et thoro, or divorce from bed-and-board) is a legal process by which a married couple may formalize a de facto separation while remaining legally married. A legal separation is granted in the form of a court order. In cases where children are involved, a court order of legal separation often makes child custody arrangements, specifying sole custody or shared parenting, as well as child support.

In the United States of America, a legal separation may address the division of assets, division of debts, child custody, child support, and alimony. A separate maintenance agreement is not a legal separation and therefore child support and custody are typically not allowed to be addressed. A separate maintenance agreement is often confused with a legal separation which is filed with a court. Separate maintenance agreements are contracts between spouses and not approved by a court. They are similar to prenuptial agreements

Under the law of some states, a separation can occur by judicial decree, or by an acknowledged agreement of the parties. In some states, there must be grounds or a cause of action to get a judicial decree of separation, such as "cruel and inhuman treatment, abandonment, neglect or refusal to support, adultery by the defendant, or confinement of the defendant in prison. Reconciliation is allowed. So, therefore, separation is revocable; state laws may require "the joint application of the parties, accompanied with satisfactory evidence of their reconciliation by the court which rendered it, subject to such regulations and restrictions as the court thinks fit to impose.

Some couples obtain a legal separation as an alternative to a divorce, based on moral or religious objections to divorce. Legal separation does not automatically lead to divorce. The couple might reconcile, in which case they do not have to do anything in order to continue their marriage.