The Netherlands has had three female Kings in a row in recent history. The Consitution is quite clear the topic: the monarch is King, and King (written) may be read as "Queen" if a woman is monarch. This led to an interesting discussion about downgrading the title of Queen as consort of the King to Princess, in analogy to Prince for the consort of a regnant Queen, because people have gotten so used to equating "King" and "Queen". And in common parlance both King and Queen were used for Beatrix: without qualification it is "Queen", but it is for instance "the first Dutch King that [..]".