As far as is known, none of the twelve disciples was martyred. The only death documented outside the Bible is the stoning of James, brother of Jesus, reported by the Jewish hi
…storian, Josephus. A remarkably similar story is also told in Acts of the Apostles about the stoning of Stephen, although Raymond E. Brown ( An Introduction to the New Testament ) says that we can never verify the existence and martyrdom of Stephen. A second-century tradition, attributed to Pope Anicetus (156-166), was that Peter was beheaded in Rome, while a later tradition was that Peter was crucified upside down in 64 CE. Acts of the Apostles mentions the imprisonment and miraculous release of Peter, but does not say anything about his subsequent death, even though the book was written around the end of the century, long after Peter would have died. Another tradition is that Paul was executed on the same day as Peter. Clement of Rome, who should have known of these events, in writing in general terms of the life and death of Peter ( 1 Clement , c. 95 CE) seems to have been unaware that Peter was ever in Rome or had been executed. Clement also appears to have believed that Paul eventually travelled to Spain. Other Christian traditions gradually grew up over the centuries, attributing gory deaths to most of the apostles, proof of their faith which could only have come from a personal knowledge of Jesus. The only disciple that tradition allows to escape martyrdom and die at a very old age was John. ( Full Answer )