Olga (Russian: Ольга also called Olga Prekrasa, or Olga the Beauty, Norse: Helga) (died July 11, 969 in 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. 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 Helene (Russian: 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.

Edward Gibbon upon Olga's conversion

Photius of Constantinople, a patriarch, whose ambition was equal to his curiosity, congratulates himself and the Greek church on the conversion of the Russians. Those fierce and bloody Barbarians had been persuaded, by the voice of reason and religion, to acknowledge Jesus for their God, the Christian missionaries for their teachers, and the Romans for their friends and brethren. His triumph was transient and premature. In the various fortune of their piratical adventures, some Russian chiefs might allow themselves to be sprinkled with the waters of baptism; and a Greek bishop, with the name of metropolitan, might administer the sacraments in the church of Kiow, to a congregation of slaves and natives. But the seed of the gospel was sown on a barren soil: many were the apostates, the converts were few; and the baptism of Olga may be fixed as the aera of Russian Christianity.

A female, perhaps of the basest origin, who could revenge the death, and assume the sceptre, of her husband Igor, must have been endowed with those active virtues which command the fear and obedience of Barbarians. In a moment of foreign and domestic peace, she sailed from Kiow to Constantinople; and the emperor Constantine Porphyrogenitus has described, with minute diligence, the ceremonial of her reception in his capital and palace. The steps, the titles, the salutations, the banquet, the presents, were exquisitely adjusted to gratify the vanity of the stranger, with due reverence to the superior majesty of the purple. In the sacrament of baptism, she received the venerable name of the empress Helena; and her conversion might be preceded or followed by her uncle, two interpreters, sixteen damsels of a higher, and eighteen of a lower rank, twenty-two domestics or ministers, and forty-four Russian merchants, who composed the retinue of the great princess Olga.

After her return to Kiow and Novogorod, she firmly persisted in her new religion; but her labours in the propagation of the gospel were not crowned with success; and both her family and nation adhered with obstinacy or indifference to the gods of their fathers. Her son Swatoslaus was apprehensive of the scorn and ridicule of his companions; and her grandson Wolodomir devoted his youthful zeal to multiply and decorate the monuments of ancient worship. The savage deities of the North were still propitiated with human sacrifices: in the choice of the victim, a citizen was preferred to a stranger, a Christian to an idolater; and the father, who defended his son from the sacerdotal knife, was involved in the same doom by the rage of a fanatic tumult.

Yet the lessons and example of the pious Olga had made a deep, though secret, impression in the minds of the prince and people: the Greek missionaries continued to preach, to dispute, and to baptize: and the ambassadors or merchants of Russia compared the idolatry of the woods with the elegant superstition of Constantinople. They had gazed with admiration on the dome of St. Sophia: the lively pictures of saints and martyrs, the riches of the altar, the number and vestments of the priests, the pomp and order of the ceremonies; they were edified by the alternate succession of devout silence and harmonious song; nor was it difficult to persuade them, that a choir of angels descended each day from heaven to join in the devotion of the Christians.