A morganatic marriage is a type of marriage which can be contracted in certain countries, usually between people of unequal social rank, which prevents the passage of the husband's titles and privileges to the wife and any children born of the marriage. It is also known as a left-handed marriage because in the wedding ceremony the groom held his bride's right hand with his left hand instead of his right.

Generally, this is a marriage between a male of high birth (i.e., from a royal or reigning house), and a woman of lesser status (a non-royal or non-reigning house, or a woman with a profession that is traditionally considered lower-status). 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. It was also practiced by the polygamous Mongols as to their non-principal wives.

It is also possible for a woman to marry a man of lower rank morganatically, but this is extremely rare as women of high rank traditionally did not have titles that they could pass to their children, and in most cases they did not choose their own husbands.