Sigfrid is said to have been born in Glastonbury, England in the second half of the 10th century. It is said that St. [[Alphege]], [[Archbishop of Canterbury]], converted him to the Christian faith. Sigfrid was an eminent priest in York who was sent by the legendary ''King Mildred'' to assist in the Christianization of Scandanavia. It is theorized that this could have been King Æthelred II the Unready.
At the behest of Olaf I Tryggvason, Sigfrid arrived in Norway in 995 with his three nephews who were Cluniac [[monks]]: Unaman the [[priest]], Sunaman the [[deacon]], and Winaman the [[subdeacon]]. There he became a court bishop for the Norwegian King. Due to the Battle of Svolder of 999-1000, Sigfrid and his nephews left for Sweden in 1002 where they founded three churches in Västergötland (West Gothland). This area was already being Christianized by the bishop Odinkar Hvite the Elder, who was based in Skara. Thus Sigfrid and his nephews went east to the region of Värend in Småland to continue their missionary efforts, erecting first a cross and then building a wooden [[church]] on the shores of Växjö Lake.
Soon, twelve prominent men of the area were soon brought to the Christian faith and [[baptism|baptized]] in a spring near the mountain Ostrabo. Their influence began a steady stream of pilgrims, who flocked to hear the Word of God and gaze upon Sigfrid's silken [[vestments]], gold and silver vessels, and other beautiful objects brought with him from England. In 1008, Sigfrid baptized King Olof Skötkonung in a spring near the village of Husaby. Olof Skötkonung became the first Christian King of Sweden, which marked the beginning of the Christianization of Sweden. Sigfrid next traveled north to re-establish the See of Upsala that had been founded by St. [[Ansgar]], but the reversion to paganism was too strong in the region and he left in failure. In 1014, Olof Skötkonung assisted Sigfrid in the establishment of the Diocese of Skara, which became a suffragan of the Archdiocese of Hamburg-Bremen. The first diocesan bishop, a German named Thurgaut, was consecrated by Sigrid. At this time, the diocese was comprised of "the Goth lands" Västergötland and Östergötland (East Gothland), some of Småland, and also a chunk of other surrounding counties. Sigfrid is said to have consecrated a [[vicar bishop]] for the eastern half of the diocese in the city of Linköping in Östergötland.