Elena Glinskaya ruled what would become Russia as regent for her son, wisely and ably in fact, until her life and reign were brought to brutal ends.
Elena Glinskaya: Powerful and Poisoned Regent
Amalasuntha: Wise Queen of the Ostrogoths
Amalasuntha ruled Rome after the Roman Empire's fall. She is known for being a wise leader of the Ostrogoths, first as regent, then as the ruling monarch.
Alice Perrers: The Manipulative Mistress
Alice Perrers was quite the ambitious mistress, though we have to have some sympathy for her—she has been hated in her time and ever since.
Almost-Queens: Anne Hyde: Mother of Two Queens-Regnant
Anne Hyde nearly became Queen of England but died before her chance to. She was a commoner who, through good luck, became the mother of Queens Mary II and Anne.
The Royal Women 