Mary, also known as Maria of Anjou, reigned as Queen of Hungary and Croatia between 1382 and 1385, and from 1386 until her death. She was the daughter of Louis the Great, King of Hungary and Poland, and his wife, Elizabeth of Bosnia. Mary's marriage to Sigismund of Luxembourg, a member of the imperial Luxembourg dynasty, was already decided before her first birthday. A delegation of Polish prelates and lords confirmed her right to succeed her father in Poland in 1379.

A queen regnant is a female monarch, equivalent in rank, title and position to a king. She reigns suo jure over a realm known as a kingdom; as opposed to a queen consort, who is married to a reigning king; or a queen regent, who is the guardian of a child monarch and rules pro tempore in the child's stead or instead of her husband who is absent from the realm, be it de jure in sharing power or de facto in ruling alone. A queen regnant is sometimes called a woman king. A princess regnant is a female monarch who reigns suo jure over a principality; an empress regnant is a female monarch who reigns suo jure over an empire.