Was Mary sinless according to Catholic teaching?

Yes. The Catholic Church teaches that Mary was preserved free from original sin from the first moment of her conception (the Immaculate Conception) and that she committed no personal sin throughout her life, by a singular grace of God in view of the merits of her Son, Jesus Christ.

The Catholic Church holds that the Virgin Mary was sinless in a unique and total way: free from original sin from the very instant of her conception, and free from all personal, actual sin throughout her earthly life. This is called the doctrine of the Immaculate Conception, defined infallibly by Pope Pius IX in 1854 but rooted in ancient Christian belief and Scripture.

This privilege was not something Mary earned; it was a grace given to her by God in anticipation of the redemption won by Christ, so that she who would bear the Savior might be a fitting and holy vessel for the Incarnation (CCC 490-492).

Scriptural Foundations

The angel Gabriel greets Mary as 'full of grace' (Luke 1:28), a title the Church understands as indicating a completeness of grace incompatible with the stain of sin. Elizabeth likewise calls her 'blessed among women' (Luke 1:42). The Church also sees Mary prefigured in Genesis 3:15, where the woman's offspring is set in permanent enmity with the serpent, suggesting she shares nothing with the corruption of sin.

While Scripture does not use the technical phrase 'Immaculate Conception,' the Church reads these passages, together with the whole tradition of Mary as the New Eve and the Ark of the New Covenant, as pointing to her singular holiness.

The Church's Teaching

The Catechism teaches that Mary was 'redeemed, in a more exalted fashion, by reason of the merits of her Son' and 'preserved immune from all stain of original sin' from the first instant of her conception (CCC 491). She also remained free from every personal sin her whole life long, by a grace granted her precisely so that she would be a worthy mother of God (CCC 493, 508).

This does not mean Mary did not need a Savior; rather, she was saved in the most perfect way possible, by preemptive redemption rather than by being cleansed after falling into sin. Her freedom from sin also underlies the doctrine of her perpetual virginity and her Assumption, since 'death has no power' where sin has left no claim.

The Church Fathers already sensed this special purity. St. Augustine, though he taught that all human beings are born under original sin, made a deliberate exception 'for the honor of the Lord' when speaking of Mary and any question of her sinning (St. Augustine, On Nature and Grace, 36).