Alexander the Great was one of the most successful military commanders of all time, securing an empire that stretched from the Mediterranean to the Himalayan Mountains. He seems to have inherited much of his moxie from mom.
Alexander's mother, Olympias, was the fourth wife of Alexander's father. Even in ancient times, Olympias got a bad rap: The historian Plutarch accused her of sleeping with snakes as part of her religious rites.
When Alexander's dad took another wife, a Macedonian named Cleopatra, Olympias went into voluntary exile, only to return after her husband was assassinated -- an event that some historians suspect Olympias had a hand in. She then had Cleopatra murdered, along with Cleopatra's infant child, helping secure her own son's succession to the throne. Olympias has also been accused of poisoning another child of Philip II, Philip III, who would survive with brain damage.
Exactly how ruthless Olympias really was is hard to say, said Brian Pavlac, a historian at King's College in Pennsylvania. Historical women often get painted as especially cruel and vicious, Pavlac told LiveScience. [Fight, Fight, Fight: The History of Human Aggression]
Cruel or not, Olympias' political mechanizations put her at odds with Macedonia's regent Antipater and his son Cassander while Alexander was off conquering the globe. Cassander's army eventually captured Olympias, and she was put to death in 316 B.C., outliving her famous son by seven years.
Isabella I, unifier of Spain
Known in U.S. history for funding Christopher Columbus' journeys, Isabella was a driving force in unifying Spain. She straightened up her inherited kingdom of Castile, instituting criminal reform and bringing down the debt left to her by her brother, the previous ruler.
She's remembered with affection today, but Isabella was "a bit ruthless," Pavlac said. Part of her strategy to unite the kingdom involved compulsory Catholicism. Muslims and Jews had to convert or flee the country. In 1480, Isabella and her husband launched the Spanish Inquisition to enforce these edicts. All that, and she had six children to boot.
Wu Zetian, China's only empress
Wu then clawed her way up to the position of Empress, by having two sons and accusing the Emperor's current (childless) wife of killing her daughter -- though some historians have wondered if Wu didn't kill the baby herself.
As the Emperor's health began to fail, Wu's influence grew. She became empress dowager and regent after he died. In 690, she broke the rules again, claiming the throne as her own, the only woman to rule China as an independent sovereign.
Unlike many of the other tradition-busting moms on this list, Wu Zetian didn't get punished for her ambition (or her tendency to murder rivals). She ruled until the age of 82, when, seriously ill and facing challenges for the throne, she relinquished power to her third son. She died soon after.
The mother of three French kings, Catherine de Medici didn't get off to a great start. An Italian married off to a French prince in love with another woman, de Medici "was at first this very marginalized person who could have been removed at any moment," Pavlac said.
But 10 years after her marriage began, she started producing heirs. When de Medici's husband, King Henry II, died, one of their sons became king at the age of 15, only to die a year later. That brought de Medici's 10-year-old son Charles IX to the throne and promoted de Medici to regent.
Catherine de Medici ruled over a France divided by civil and religious warfare. She was no political genius, Pavlac said, but "she did what she could to hold things together for her and her children."
In 1572, the Catholic Charles IX took a genocidal step, ordering Paris' city gates closed and thousands of visiting Protestants killed. Blame for the St. Bartholomew's Day Massacre, as it became known, fell into the queen mother's lap, cementing her reputation as treacherous and scheming. Nonetheless, she remained a powerful advisor to the next king, her third son Henry III.
"She was at least brighter than her sons," Pavlac said. "They made a lot of bad decisions."