An heir presumptive is a person who is first in line to inherit a title, property, or possession, if no heir apparent exists. If a ruling monarch has no children, for instance, the heir presumptive may be his or her brother or sister, or nephew or niece. If an heir apparent is born, or if an heir presumptive with better claims, such as a closer familial tie, arrives on the scene, the heir presumptive may lose his or her claim to inherit.
The concept of a presumptive heir relates to the need for titles and inheritance rights to be clearly delineated. When confusion exists over a line of succession, stable estates and even countries may quickly find themselves embroiled in civil wars between warring claimants. Establishing an heir presumptive makes it possible for titles or estates to transfer smoothly without possibility of succession disputes.
Naturally, the great downside to the use of an heir or heiress succession is that it usually has little or nothing to do with competency or ability. Many unfortunate countries have found themselves in a bad situation after a hopelessly incompetent heir assumes a throne. This very situation has lead to several historical incidences in which an heir presumptive has attempted to seize a title on the grounds that the heir apparent is doing measurable damage. Quite a few heir presumptives have found themselves favored by the local populace as a result of the heir apparent's incompetent actions.
In many common law systems, heir apparent status can be decreed only on the legitimate male children of the reigning title or estate holder. A female child can be only labeled an heir presumptive, and may easily be displaced if a male heir is born. Likewise, a male child born out of wedlock may be named as an heir presumptive and may even take precedence over legitimate females, but is usually displaced from the line of succession should a legitimate male be born.
There is a natural contention between an heir apparent and a presumptive heir that legal assurances cannot always bind, one that has repeatedly played out dramatically in both life and art. In Shakespeare's Hamlet, part of the great wrongness in Elsinore is that a person who would normally be an heir presumptive, Claudius, has assumed power over the murdered king's son and heir apparent, Hamlet. Shakespeare peppers this play with woeful musings on the ill consequences of an upset line of succession.
Shakespeare's discourse on the matter may have been spurred by a current event that caused much civil unrest in his time: the succession of the heir presumptive, King James I, to the throne of England after the death of the childless Queen Elizabeth I. Queen Elizabeth I herself was a presumptive heiress who achieved the throne at least partly through popular demand. Third in line for the English throne after the death of her father, Henry VIII, Elizabeth survived imprisonment and threats of execution at the hands of her older sister, Queen Mary I, who suspected the presumptive heiress of plotting a coup to seize the throne.