The perpetual virginity of Mary is a Christian doctrine that Mary, the mother of Jesus, was a virgin "before, during and after" the birth of Christ. In Western Christianity, the Catholic Church adheres to the doctrine, as do some Lutherans, Anglicans, Reformed, and other Protestants. Shenouda III, Pope of the Coptic Orthodox Church, affirmed the teaching, and Eastern Orthodox churches recognize Mary as Aeiparthenos, meaning "ever-virgin". It is one of the four Marian dogmas of the Catholic Church. Most modern nonconformist Protestants reject the doctrine.

The tradition of the perpetual virginity of Mary first appears in a late 2nd-century text called the Protoevangelium of James. The Second Council of Constantinople in 553 gave her the title "Aeiparthenos", meaning Perpetual Virgin, and at the Lateran Synod of 649 Pope Martin I emphasized the threefold character of the perpetual virginity, before, during, and after the birth of Christ. The Lutheran Smalcald Articles (1537) and the Reformed Second Helvetic Confession (1562) codified the doctrine of perpetual virginity of Mary as well.

The doctrine of Mary's perpetual virginity has been challenged on the basis that the New Testament explicitly affirms her virginity only until the birth of Jesus and mentions the brothers (adelphoi) of Jesus. This word only very rarely means other than a biological or spiritual sibling, and they may have been: (1) the sons of Mary, the mother of Jesus, and Joseph; (2) sons of the Mary named in Mark 15:40 as "mother of James and Joses", whom Jerome identified as a sister of Mary, the mother of Jesus; or (3) sons of Joseph by a former marriage. Further scriptural difficulties were added by Luke 2:7, which calls Jesus the "first-born" son of Mary, and Matthew 1:25, which adds that Joseph "did not know her until she had brought forth her firstborn son."