St George is the patron saint of England and among the most famous of Christian figures. But of the man himself, nothing is certainly known. Our earliest source, Eusebius of Caesarea, writing c. 322, tells of a soldier of noble birth who was put to death under Diocletian at Nicomedia on 23 April, 303, but makes no mention of his name, his country or his place of burial. According to the apocryphal Acts of St George current in various versions in the Eastern Church from the fifth century, George held the rank of tribune in the Roman army and was beheaded by Diocletian for protesting against the Emperor's persecution of Christians. George rapidly became venerated throughout Christendom as an example of bravery in defence of the poor and the defenceless and of the Christian faith.

George was probably first made well known in England by Arculpus and Adamnan in the early eighth century. The Acts of St George, which recounted his visits to Caerleon and Glastonbury while on service in England, were translated into Anglo-Saxon. Among churches dedicated to St George was one at Doncaster in 1061. George was adopted as the patron saint of soldiers after he was said to have appeared to the Crusader army at the Battle of Antioch in 1098. Many similar stories were transmitted to the West by Crusaders who had heard them from Byzantine troops, and were circulated further by the troubadours. When Richard 1 was campaigning in Palestine in 1191-92 he put the army under the protection of St George.

Because of his widespread following, particularly in the Near East, and the many miracles attributed to him, George became universally recognized as a saint sometime after 900. Originally, veneration as a saint was authorized by local bishops but, after a number of scandals, the Popes began in the twelfth century to take control of the procedure and to systematize it. A lesser holiday in honour of St George, to be kept on 23 April, was declared by the Synod of Oxford in 1222; and St George had become acknowledged as Patron Saint of England by the end of the fourteenth century. In 1415, the year of Agincourt, Archbishop Chichele raised St George's Day to a great feast and ordered it to be observed like Christmas Day. In 1778 the holiday reverted to a simple day of devotion for English Catholics.

The banner of St George, the red cross of a martyr on a white background, was adopted for the uniform of English soldiers possibly in the reign of Richard 1, and later became the flag of England and the White Ensign of the Royal Navy. In a seal of Lyme Regis dating from 1284 a ship is depicted bearing a flag with a cross on a plain background. During Edward 111's campaigns in France in 1345-49, pennants bearing the red cross on a white background were ordered for the king's ship and uniforms in the same style for the men at arms. When Richard 11 invaded Scotland in 1385, every man was ordered to wear 'a signe (sic) of the arms of St George', both before and behind, whilst death was threatened against any of the enemy's soldiers 'who do bear the same crosse or token of Saint George, even if they be prisoners'.

The fame of St George throughout Europe was greatly increased by the publication of the Legenda Sanctorum (Readings on the Saints), later known as the Legenda Aurea (The Golden Legend) by James of Voragine in 1265. The name 'golden legend' does not refer to St George but to the whole collection of stories, which were said to be worth their weight in gold. It was this book which popularized the legend of George and the Dragon. The legend may have been particularly well received in England because of a similar legend in Anglo-Saxon literature. St George became a stock figure in the secular miracle plays derived from pagan sources which continued to be performed at the beginning of spring. The origin of the legend remains obscure. It is first recorded in the late sixth century and may have been an allegory of the persecution of Diocletian, who was sometimes referred to as 'the dragon' in ancient texts. The story may also be a christianized version of the Greek legend of Perseus, who was said to have rescued the virgin Andromeda from a sea monster at Arsuf or Jaffa, near Lydda (Diospolis), where the cult of St George grew up around the site of his supposed tomb.