Olga of KievOlga
(Saint Olga, Helga)(c.880
), belonged to the Scandinavian
aristocracy in Russia (Rus'
, Varangians) and married the future Igor
, prince of Kiev
. After his death, she ruled Kievan Rus
as regent (945
) for their son, Sviatoslav I
. She spent great effort to avenge her husband's death at the hands of the Derevlians, and succeeded in slaughtering most of them. She was the first Rus ruler to convert to Christianity
, sometime between 954 and 958. However, she failed to convert Sviatoslav, and it was left to his son and successor Vladimir I
to make Christianity
the lasting state religion.