The accepted version of who St George is based on two related main sources. One source is Greek, the other is Latin.
The Greek tradition argues that the Saint was born to Christian parents, in Cappadocia (modern day Turkey). His father died fighting for his faith and whilst still a child, George fled with his mother to Palestine. Growing up in Palestine exposed George to the Roman culture and he eventually joined the Roman army. At the outbreak of the Roman Emperor Diocletian's persecution of Christians, George declared himself a Christian. For his faith he was sentenced to death. In true Roman fashion George was subjected to numerous grisly tortures all of which he miraculously survived. By making the sign of the cross George apparently caused all the statues of the gods to fall at his feet. This later miracle persuaded the Empress Alexandra to convert to Christianity. This conversion proved too much for Diocletian, Alexandra was sentenced to death. George was decapitated. The date was 23 April AD 303.
The Latin version of the story is very similar to its Greek counterpart.
The Emperor Diocletian has become Dacian, the Emperor of the Persians. George in this account lives and dies in Melitene, in Eastern Cappadocia. He is similarly tortured, but his miraculous survival of the numerous tortures results in the conversion to Christianity of 40,900 people. George is put to death by Dacian, but Dacian himself dies, when a whirlwind of fire carries him off.
In AD 494, Pope Gelasius whilst rejecting the more unrealistic aspects of the St George legend, declared him a Saint. One of those "whose names are justly reverenced among men, but whose actions are known only to God".