How many of Jesus original Apostles were martyred?

All of them; although not all of the deaths of the Apostles are documented in the Bible. Many of the deaths of the Apostles can, however, be found in extra-biblical records. The deaths of the original Apostles of Christ are as follows: In A.D. 34, a repentant Judas Iscariot crucified himself in Palestine by hanging (Matthew 27:3–4). In A.D. 44, James the Greater was beheaded by a sharpened sword in Judea by the orders of Herod Agrippa. In the year A.D. 54, Philip was scourged and crucified in Heliopolis, Egypt. In the year A.D. 67, Paul was beheaded by Emperor Nero in Rome, Italia; Simon Peter was crucified upside down (at his request) by Emperor Nero in Rome, Italia also in the year A.D. 67 (John 21:19). In the year A.D. 69, Andrew was crucified in Western Greece on an “X” shaped cross and lived for two days thereon; also in the year A.D. 69, James the Just was thrown off of the pinnacle of the temple of Jerusalem and beaten to death with a club. Bartholomew was skinned alive and beheaded. Thomas was run through by a sharpened spear. Matthew was stabbed in the back with a sharpened sword by the orders of King Hertacus of Ethiopia. Thaddeus was crucified in Edessa, Asia Minor in A.D. 72. Simon the Canaanite was crucified in England in A.D. 74. James the Less was beaten in the head with a large club during a riot circa A.D. 90. John the Revelator was exiled to Patmos and died in his old age as a prisoner in A.D. 100. All of the Apostles of Jesus Christ met violent ends, and it is a true testament to the conditions that existed for the early Christians of the first century Roman Empire.