Queen mother is a title or position reserved for a widowed queen consort (a queen dowager) whose son or daughter from that marriage is the reigning monarch. The term has been used in England since at least 1577. The title arises in hereditary monarchies.
A queen as bride of the king has a royal position of great importance, but does not normally have any rights to succeed him to rule as monarch after the king's death.
The queen's eldest son would normally be crowned as successor upon the king's death, often leaving the new king's mother still alive, but no longer holding any official position. The new king, of course, might already be married, or marry subsequently, and would have his own queen.
Therefore, the title of "queen mother" identifies the widow of the deceased former king, and mother of the currently reigning king or queen. The title distinguishes the queen mother from the current queen, who is the wife of the currently reigning king. It also distinguishes such a person from a mother of the monarch who was not previously queen. For example, Victoria, the Duchess of Kent and Strathearn was "the Queen's mother" when her daughter became queen but not "queen mother".
Another type of queen mother is produced when a queen regnant abdicates in favour of her heir presumptive. Queen Juliana of the Netherlands is an example: after her abdication she was officially styled as Her Majesty Juliana, Queen Mother of the Netherlands, but she wished to be known as HRH Princess Juliana of the Netherlands.
As the king's or queen's mother, the queen mother is typically supported throughout her remaining years and given honour as a beloved relative, but had no official position or power and was expected to carefully abstain from any involvement in governance or politics.
The following queens became queen mothers, though not all chose to use that style.
See main article: English and British Queen mothers.
The title queen mother has been widely used. Other well-known queen mothers include:
Diana, Princess of Wales reportedly once suggested to journalist Andrew Morton (author of Diana: Her True Story) that when her son, Prince William of Wales became king, she would be known as King Mother. No such designation has ever officially existed, nor is there independent evidence that such terminology was ever considered. Queen mother means "queen who is mother to the current monarch", not "mother of the queen"; "king mother" is a contradiction in terms.
In the event that a queen regnant were to die and leave her husband a widowed bachelor, then like a queen consort, a king consort could also be styled "king father".
Similarly, if a king were to abdicate and pass the throne to his child, then in that case the king could have his son or daughter style him as a king father. King Norodom Sihanouk of Cambodia was styled as HM King-Father Norodom Sihanouk when he abdicated in favor of his son.