Olav the Holy, also known as Saint Olav, was a king of Norway who reigned from 1015 to 1028. He is best known for his efforts to convert Norway to Christianity, which significantly influenced the country's religious landscape. His reign was marked by battles to unify Norway and establish a centralized monarchy. After his death in battle in 1030, Olav was canonized as a saint by the Catholic Church. His legacy includes the founding of the city of Oslo and the establishment of St. Olav's Day, celebrated on July 29, which honors his contributions to Norway's Christian heritage.