It has been said so often that it has now become accepted as fact that, at his conversion, God changed Saul’s name to Paul to signify his new identity in Christ. It seems almost heretical to say this, but there is no evidence for that whatsoever and it is simply not true. The truth is that Saul was always Paul as well.
Saul was his Jewish name which would, in all probability, have been given to him when he was circumcised on the eighth day after birth (Philippians 3:5). John Pollock suggests that it might have been chosen for him “either for its meaning, “asked for”, or in honour of the most famous Benjaminite in history, King Saul.” (The Apostle Tring: Lion Publishing, 1969 p5)
He would also, at birth, have been given a Roman name, which was Paulus – Paul in the Greek – which is why, as the Scripture says, “Saul, who was also called Paul” (Acts 13:9).
The reason for the perceived name change is not because of his conversion but because of his ministry. After all, Scripture still calls him Saul at least 14 years after his conversion; but the change takes place at that point in Acts 13 when Saul and Barnabas are in Cyprus on their first missionary. It would seem that Saul himself, and his biographer Luke, thought it would be more appropriate to use his Roman name, rather than his Jewish one, as he began to travel further and further abroad into the Gentile world.
I must admit that I also like the theory, whether factual or not, that Paul gave up the use of his Hebrew name with its royal significance, preferring to use his Roman name which meant little or small, reflecting his desire to be seen as small in comparison to the infinitely greater Christ he lived – and ultimately died – to serve.