Urraca of León and Castile: She inherited Urraca's second marriage was intended to unite into a single Spain the separate kingdoms of León, Castile and Aragon. The marriage was not successful and many blamed the civil war that followed on her being a woman ruler. She was queen regnant from 1109 to 1126 in León, Castile and Galicia.
Empress Matilda: as her tomb inscription notes, she was the daughter, wife and mother of three Henry's. She was designated as the heir of her father, Henry I, King of England, but her cousin usurped the throne and civil war followed. Matilda (also called Maud) briefly prevailed over her cousin in 1141, but was never crowned.
Eleanor of Aquitaine: though she was queen consort to kings first of France then of England, she was the ruler in her own right (1137 - 1204) of the vast duchy of Aquitaine. She supported a rebellion of her sons against their father, and her husband, Henry II of England, imprisoned her when he defeated the rebels.
Image: 12th Century frescoes showing rulers of Leon and Castile, San Isadoro Basilica, Leon, Spain: Luis Castaneda Inc. / Getty Images