Morganatic marriage, sometimes called a left-handed marriage, is a marriage between people of unequal social rank, which in the context of royalty or other inherited title prevents the principal's position or privileges being passed to the spouse, or any children born of the marriage. The concept is most prevalent in German-speaking territories and countries most influenced by the customs of the German-speaking realms.

Generally, this is a marriage between a man of high birth (such as from a reigning, deposed or mediatised dynasty) and a woman of lesser status (such as a daughter of a low-ranked noble family or a commoner). Usually, neither the bride nor any children of the marriage have a claim on the bridegroom's succession rights, titles, precedence, or entailed property. The children are considered legitimate for all other purposes and the prohibition against bigamy applies. In some countries, a woman could also marry a man of lower rank morganatically. As a result of the above, a king deciding to enter into a morganatic marriage who does not have children from a previous marriage thereby gives up the chance of being succeeded by his own children and accepts that succession would pass to his other relatives.