Primogeniture is the right, by law or custom, of the firstborn to inherit the entire estate, to the exclusion of younger siblings (compare to ultimogeniture). Historically, the term implied male primogeniture, to the exclusion of females.^{[citation needed]} According to the Norman tradition, the first-born son inherited the entirety of a parent's wealth, estate, title or office and then would be responsible for any further passing of the inheritance to his siblings. In the absence of children, inheritance passed to the collateral relatives, in order of seniority of the males of collateral lines. The eligible descendants of deceased elder siblings take precedence over living younger siblings, such that inheritance is settled in the manner of a depth-first search.

The principle has applied in history to inheritance of real property (land) and inherited titles and offices, most notably monarchies.

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 with the wider promotion of feminism, eliminate the preference for male over female siblings. Six monarchies in Europe have eliminated male preference: Sweden, Norway, Netherlands, Belgium, Denmark and Luxembourg.