Primogeniture (English pronunciation: /praɪməˈdʒɛnᵻtʃər/) is the right, by law or custom, of the legitimate, son to inherit his parent's entire or main estate, in preference to daughters, elder illegitimate sons, younger sons and collateral relatives. The son of a deceased elder brother inherits before a living younger brother by right of substitution for the deceased heir. In the absence of any children, brothers succeed, individually, to the inheritance by seniority of age (subject to substitution). Among siblings, sons inherit before daughters. In the absence of male descendants in the male-line, there are variations of primogeniture which allocate the inheritance to a daughter or a brother or, in the absence of either, to another collateral relative, in a specified order (e.g. male-preference primogeniture, Salic primogeniture, semi-Salic primogeniture).
The principle has applied in history to inheritance of real property (land) as well as inherited titles and offices, most notably monarchies, continuing until modified or abolished.
Variations on primogeniture modify the right of the first-born son to the entirety of a family's inheritance (see appanage) or, in the West since World War II, eliminate the preference for males over females (absolute primogeniture). Most monarchies in Europe have eliminated male preference in succession: Belgium, Denmark, Luxembourg, Netherlands, Norway, Sweden and the United Kingdom.