Helena - Mother of Constantine
St. Helena was the influential mother of the Roman emperor Constantine the Great.
Roman Emperors - St. Helen
From De Imperatoribus Romanis, a biography of Constantine's mother, Flavia Iulia Helena. Helena's origins are obscure and we don't know whether she was originally Christian, but she did convert and made a trip to Palestine and the East where she is credited with, but probably did not discover the Cross.
Lives of the Saints version of Constantine's mother's life. Attributes Helena's Christianity to her son's conversion after which she had shrines and churches built.
Saint Helen of Caernarvon or Elen Luyddog was a legendary Welsh princess who is sometimes confused with Constantine's mother because they were both mothers of Constantines.