Morganatic marriage, sometimes called a left-handed marriage, is a marriage between people of unequal social rank, which in the context of royalty prevents the passage of the husband's titles and privileges to the wife and any children born of the marriage.
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.
After World War I the heads of both ruling and formerly reigning dynasties initially continued the practice of rejecting dynastic titles and/or rights for descendants of "morganatic" unions, but gradually allowed them, sometimes retroactively, effectively de-morganatizing the wives and children. This was accommodated by Perthes' Almanach de Gotha (which categorised princely families by rank until it ceased publication after 1944) by inserting the offspring of such marriages in a third section of the almanac under entries denoted by a symbol (a dot within a circle) that "signifies some princely houses which, possessing no specific princely patent, have passed from the first part, A, or from the second part into the third part in virtue of special agreements." The Fürstliche Häuser ("Princely Houses") series of the Genealogisches Handbuch des Adels ("Genealogical Manual of the Nobility") has followed this lead, likewise enrolling some issue of unapproved marriages in its third section, "III B", with a similar explanation: "Families in this section, although verified, received no specific decree, but have been included by special agreement in the 1st and 2nd sections".
Variations of morganatic marriage were also practised by non-European dynasties, such as the Royal Family of Thailand, the polygamous Mongols as to their non-principal wives, and other families of Africa and Asia.