St. Paul, also known as the Apostle Paul, was a significant figure in early Christianity. He was originally known as Saul and was a persecutor of Christians before he experienced a dramatic conversion to Christianity. After his conversion, he became a fervent preacher and missionary, traveling extensively to spread the teachings of Jesus Christ. He is credited with writing several of the books in the New Testament of the Bible and played a crucial role in the development and spread of early Christian communities. St. Paul is revered as a saint in many Christian traditions and is considered one of the most influential figures in the history of Christianity.