A legal obligation on a person to provide financial support to their spouse before or after marital separation or divorce. The obligation arises from the divorce law or family law of each country. In most jurisdictions, it is distinct from child support, where, after divorce, one parent is required to contribute to the support of their children by paying money to the child's other parent or guardian.

The modern concept of alimony is derived from English ecclesiastical courts that awarded alimony in cases of separation and divorce. Alimony pendente lite was given until the divorce decree, based on the husband's duty to support the wife during a marriage that still continued. Post-divorce or permanent alimony was also based on the notion that the marriage continued, as ecclesiastical courts could only award a divorce a mensa et thoro, similar to a legal separation today. As divorce did not end the marriage, the husband's duty to support his wife remained intact.

Where a divorce or dissolution of marriage (civil union) is granted, either party may ask for post-marital alimony. It is not an absolute right, but may be granted, the amount and terms varying with the circumstances. If one party is already receiving support at the time of the divorce, the previous order is not automatically continued (although this can be requested), as the arguments for support during and after the marriage can be different. Unless the parties agree on the terms of their divorce in a binding written instrument, the court will make a determination based on the legal argument and the testimony submitted by both parties. This can be modified at any future date based on a change of circumstances by either party on proper notice to the other party and application to the court. The courts are generally reluctant to modify an existing agreement unless the reasons are compelling. In some jurisdictions the court always has jurisdiction to grant maintenance should one of the former spouses become a public charge.