The Cross of St. Peter or Petrine Cross is an inverted Latin cross traditionally used as a Christian symbol, but in recent times also used widely as an anti-Christian symbol (a meaning which is not valid with respect to traditional conventions of Christian symbolism).

The origin of this symbol comes from the Catholic tradition that Simon Peter was crucified upside down, as told by Origen of Alexandria. The tradition first appears in the "Martyrdom of Peter", a fragmented text found in, but likely predating, the apocryphal Acts of Peter, which was written no later than 200 A.D. It is believed that Peter requested this form of crucifixion as he felt he was unworthy to be crucified in the same manner that Jesus died. As such, some Catholics use this cross as a symbol of humility and unworthiness in comparison to Jesus.

According to Roman Catholicism, the Pope is Peter's successor as Bishop of Rome. Therefore the Papacy is often represented by symbols that are also used to represent Peter — one example being the Keys of Heaven, another the Petrine Cross. During Pope John Paul II's visit to Israel, he sat on a chair with the Cross of Peter cut into the back.

Saint Peter or Simon Peter was an early Christian leader and one of the twelve apostles of Jesus who is featured prominently in the New Testament Gospels and the Acts of the Apostles and who is venerated as a saint. The son of John or of Jonah, he was from the village of Bethsaida in the province of Galilee or Gaulanitis. His brother Andrew was also an apostle. Peter is venerated in multiple churches and is regarded as the first Pope by the Catholic Church. After working to establish the church of Antioch, presiding for seven years as the leader of the city's Christian community, he preached to scattered communities of believers, Jews, Hebrew Christians and the gentiles, in Pontus, Galatia, Cappadocia, Asia Minor and Bithynia.^{[citation needed]} He then went to Rome, where in the second year of Claudius, it is claimed, he overthrew Simon Magus and held the Sacerdotal Chair for 25 years.^{[citation needed]} He is said to have been put to death at the hand of Emperor Nero.

Peter wrote two General epistles. The Gospel of Mark is also ascribed to him (as Mark was his disciple and interpreter). On the other hand, several books bearing his name—the Acts of Peter, Gospel of Peter, Preaching of Peter, Revelation of Peter, and Judgement of Peter—are rejected by the Catholic Church as Apocryphal.