Paul’s original name before his conversion was Saul. In the New Testament, he is identified as Saul during the road-to-Damascus episode, when he encounters the risen Jesus and later receives help from Ananias. Saul is a Greek form of the Hebrew name associated with Israel’s first king, Saul of Kish, and Paul belonged to the tribe of Benjamin.
The name change was not necessarily a dramatic renaming at the moment of conversion. Acts 13:9 says, “Saul, who was also called Paul,” showing that he used both names. Saul was his Jewish name, while Paul was his Roman name, a practical combination for a Jewish man from the Roman city of Tarsus who later preached extensively among Gentiles.
A common mix-up is the idea that Paul changed from Saul immediately after converting. Acts continues to call him Saul during the early part of his ministry, and the name Paul becomes prominent during his first missionary journey. In his own surviving letters, he consistently calls himself Paul.