A morganatic marriage is a type of marriage which can be contracted in certain countries, usually between persons of unequal social rank (unebenbürtig in German), which prevents the passage of the husband's titles and privileges to the wife and any children born of the marriage.

Often, this is a marriage between a male from a royal or reigning house, often a historical German state, and a woman of lesser status (a non-royal or reigning house, or a woman with a low-status profession such as actress). Neither the bride nor any children of the marriage has any claim on the groom's titles, rights, or entailed property. The children are considered legitimate on other counts and the prohibition of bigamy applies.

Morganatic, from the Latin phrase matrimonium ad morganaticam, refers to the gift given by the groom to the bride on the morning after the wedding. The practice of morganatic marriage was most common in the German-speaking parts of Europe, where equality in marriage was considered an important principle among the reigning houses and high nobility. The German name was Ehe zur linken Hand (marriage by the left hand) and the husband gave his left hand during the wedding ceremony instead of the right.

Marriages have never been considered morganatic in England, Great Britain, or the United Kingdom. The French equivalent was an (openly) secret marriage.

Examples of morganatic marriage:

• Franz Ferdinand of Austria and Countess Sophie Chotek von Chotkowa. The bride was made Princess (later Duchess) of Hohenberg by Franz Josef. Their children took their mother's name and rank, and were excluded from the imperial succession.

• Prince Alexander of Hesse, son of the Grand Duke of Hesse and the Rhine, and Countess Julia von Hauke. The Grand Duke made the bride Princess of Battenburg, and the resulting family provided a ruler of Bulgaria and royal consorts for Spain and the United Kingdom.

• Prince Alexander of Württemberg and Claudine Rhedey. She was made Countess of Hohenstein; their children were later granted the title of Prince of Teck. The eldest son, Franz, was later made Duke of Teck. His daughter Mary of Teck married George V of the United Kingdom.

• Ludwig Wilhelm, Duke in Bavaria and (actress) Henriette Mendel. She was created Freifrau von Wallersee, and their daughter, Marie Louise, Countess Larisch von Moennich, was a confidante of Empress Elisabeth ("Sissi") of Austria.

• Louis XIV of France married Madame de Maintenon in secret.

• Tsesarevich Constantine Pavlovich, Governor of Poland, was excluded from succession for having married a Polish countess.

• Archduke Ferdinand II of Austria, Regent of the Tyrol

The marriage of the former King Edward VIII and Wallis Simpson was not morganatic, which concept does not exist in British law. Edward renounced all of his titles for himself and successors when he abdicated, and was created Duke of Windsor. When he married his wife became Duchess, and any children would have inherited the title. The syle HRH is in the sovereign's gift, and was specifically not granted to Wallis Simpson or any future children. It has been suggested that similar arrangements could be cobbled together for Prince Charles, Prince of Wales and Camilla Parker-Bowles should they wish to be married and objections to her bearing specific titles remain strong.

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