Ignatius of Antioch (/ɪɡˈneɪʃəs/; Ancient Greek: Ἰγνάτιος Ἀντιοχείας, romanized: Ignátios Antiokheías; died c. 108/140), also known as Ignatius Theophorus (Ἰγνάτιος ὁ Θεοφόρος, Ignátios ho Theophóros, 'the God-bearing'), was an early Christian writer and Patriarch of Antioch. While en route to Rome, where he met his martyrdom, Ignatius wrote a series of letters. This correspondence forms a central part of a later collection of works by the Apostolic Fathers. He is considered one of the three most important of these, together with Clement of Rome and Polycarp. Although the authenticity of his letters has been questioned, they continue to serve as an example of early Christian theology, and address important topics including ecclesiology, the sacraments, and the role of bishops.

Nothing is known of Ignatius' life apart from the words of his letters and later traditions. It is said Ignatius converted to Christianity at a young age. Tradition identifies him and his friend Polycarp as disciples of John the Apostle. Later, Ignatius was chosen to serve as Bishop of Antioch; the fourth-century Church historian Eusebius writes that Ignatius succeeded Evodius. Theodoret of Cyrrhus claimed that St. Peter himself left directions that Ignatius be appointed to this episcopal see. Ignatius was called Theophorus (God Bearer). A tradition exists that he was one of the children whom Jesus Christ took in his arms and blessed.

Ignatius' feast day was kept in his own Antioch on 17 October, the day on which he is now celebrated in the Catholic Church and generally in western Christianity, although from the 12th century until 1969 it was put at 1 February in the General Roman Calendar.

In the Eastern Orthodox Church it is observed on 20 December. The Synaxarium of the Coptic Orthodox Church of Alexandria places it on the 24th of the Coptic Month of Koiak (which is also the 24th day of the fourth month of Tahisas in the Synaxarium of the Ethiopian Orthodox Tewahedo Church), corresponding in three years out of every four to 20 December in the Julian Calendar, which currently falls on 2 January of the Gregorian Calendar.

Ignatius is honored in the Church of England and in the Episcopal Church on 17 October. Likewise, Lutheran Churches honor Ignatius on 17 October.

Ignatius was condemned to death for his faith, but instead of being executed in his home town of Antioch, the bishop was taken to Rome by a company of ten soldiers:

'From Syria even unto Rome I fight with beasts, both by land and sea, both by night and day, being bound to ten leopards, I mean a band of soldiers...'

— Ignatius to the Romans Chapter 5