Saint Olga (also called Olga Prekrasa, or Olga the Beauty, Old Norse: Helga; died July 11, 969, Kiev) was a Pskov woman of Varangian extraction who married the future Igor of Kiev, arguably in 903.

The Primary Chronicle gives 879 as her date of birth, which is rather unlikely, given the fact that her only son Svyatoslav was probably born some 65 years after that date. She spent great effort to avenge her husband's death at the hands of the Drevlians, and succeeded in slaughtering many of them and interring some in a ship burial, while still alive. She is reputed to have scalded captives to death and another, probably apocryphal, story tells of how she destroyed a town hostile to her. She asked that each household present her with a dove as a gift, then tied burning papers to the legs of each dove which she then released to fly back to their homes. Each avian incendiary set fire to the thatched roof of their respective home and the town was destroyed. After Igor's death, she ruled Kievan Rus as regent (945-c.963) for their son, Svyatoslav.

She was the first Rus ruler to convert to Christianity, either in 945 or in 957. The ceremonies of her formal reception in Constantinople were minutely described by Emperor Constantine VII in his book De Ceremoniis. After her baptism she took the Christian name Yelena, after the reigning Empress Helena Lekapena.

Olga was one of the first people of Rus to be proclaimed saint, for her efforts to spread the Christian religion in the country. However, she failed to convert Svyatoslav, and it was left to her grandson and pupil Vladimir I to make Christianity the lasting state religion.