Of course there have been woman rulers for a long time, whether dubbed queen, czarina or other title.
I suppose I should differentiate between someone named as queen, wife (sometimes consort) of the king, and someone who serves as monarch. For instance, in Jordan, when American-born Lisa Halaby married King Hussein, she became Queen Noor when she converted to Islam. But when Hussein died in 1999, and his son by a previous marriage became King Abdullah II, Abdullah’s wife became Queen Rania, with Noor becoming queen dowager.
As far as I can tell – and please correct me if I’m wrong – there are only three current queen monarchs: Queen Margrethe II of Denmark (pictured above), Queen Beatrix of the Netherlands (pictured to the right), and the one who just turned 85.
The rules of male primogeniture had been in place for many years in most countries, which meant that the only way a female could become a monarch queen is if her father had no sons whatsoever. This is, of course the case for the world’s best known current female monarch, Queen Elizabeth II, whose father George VI had two daughters, she and Margaret, and no sons.
The rules of primogeniture, though are changing. “Five monarchies in Europe have eliminated male preference: Sweden, Norway, Netherlands, Belgium and Denmark.” However, the Norwegian change is not retroactive, and therefore does not affect the current succession where a younger male is ranked over an older female.
Spain and the United Kingdom are also considering the change; however, for the latter, this would require changes in the law in not only the UK, but the 15 other Commonwealth realm countries of Antigua and Barbuda, Australia, the Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, the Solomon Islands, and Tuvalu.