When Could Women Rule England as Queen?

The first woman to officially reign as Queen Regnant (sovereign in her own right) was Mary I (1553–1558).

Precedents:

• Empress Matilda (1102–1167): Named heir by Henry I (1126); briefly controlled London (1141) during the Anarchy but never crowned. Styled "Lady of the English."
• Lady Jane Grey (1537–1554): "Nine Days' Queen" (1553)—proclaimed by coup, deposed, executed. Not universally recognized.

Mary I's Parliament passed the Act Concerning Regal Power (1554), affirming a queen regnant holds identical authority to a king. Elizabeth I (1558–1603) solidified the precedent. Since then, six queens regnant have ruled (Mary II, Anne, Victoria, Elizabeth II).