The first woman considered to be Queen-Regnant of England, though her reign is disputed, was Matilda, formerly Empress of Germany. Her mother was Matilda of Scotland.
Almost-Queens: Matilda of Scotland

The first woman considered to be Queen-Regnant of England, though her reign is disputed, was Matilda, formerly Empress of Germany. Her mother was Matilda of Scotland.
Blanche of Castile served as regent of France on two occasions and held great power in the country even when she wasn’t ruling.
Rosamund Clifford (c. 1150 - c. 1176) was Henry II of England's mistress. Unluckily for her, his wife was Eleanor of Aquitaine, who was not at all fond of The Fair Rosamund.
Berengaria of Navarre became Queen of England in the 1100s, but because her husband was always on crusade, she never got to settle down in England.