Princess Olga the Beautiful lived between 890-969. For almost twenty years she ruled Kievan Rus. Her very first act as a ruler was to take a bloody revenge against Drevlians, the people who had killed her husband, prince Igor. She burned down an entire town with all its citizens because her rage was so great.
At the age of 45, Princess Olga gave birth to her only child and ruled in his name until he became an adult. She was a very active ruler who traveled incessantly around the country, trying to improve life in her realm. Emperor Constantine of Constantinople kept asking her to marry him but Olga remained faithful to the memory of her dead husband.
She was also the very first ruler of Kiev who converted to Christianity. The Orthodox Church proclaimed Olga a saint and considers her to be equal to the Apostles. The name "Olga" actually means "a saint", so she was obviously destined for sainthood from the very beginning.