Catherine of Alexandria, also spelled Katherine, was, according to tradition, a Christian saint and virgin, who was martyred in the early 4th century at the hands of the emperor Maxentius. According to her hagiography, she was both a princess and a noted scholar who became a Christian around age 14, converted hundreds of people to Christianity, and was martyred around age 18.

The Eastern Orthodox Church venerates her as a great martyr and celebrates her feast day on 24 or 25 November, depending on the regional tradition. In Catholicism, Catherine is traditionally revered as one of the Fourteen Holy Helpers, and she is commemorated in the Roman Martyrology on 25 November. Her feast was removed from the General Roman Calendar in 1969 but restored in 2002 as an optional memorial. In the Episcopal Church, St. Catherine is commemorated on 24 November, together with the martyrs Barbara of Nicomedia and Margaret of Antioch, while in the Church of England her feast day is 25 November.

Some modern scholars consider that the legend of Catherine was probably based on the life and murder of the virgin Saint Dorothea of Alexandria and the Greek philosopher Hypatia, with the reversed role of a Christian and neoplatonist in the case of the latter. On the other hand, Leon Clugnet writing in the Catholic Encyclopedia states "although contemporary hagiographers look upon the authenticity of the various texts containing the legend of St. Catherine as more than doubtful, it is not therefore meant to cast even the shadow of a doubt around the existence of the saint".

According to the traditional narrative, Catherine was the daughter of Sabinella and Constus (or Costus), the governor of Alexandria during the reign of the Emperor Maximian (286–305). She was a Greco-Egyptian. From a young age she devoted herself to study. A vision of the Virgin Mary and the Child Jesus persuaded her to become a Christian. When the persecutions began under the Emperor Maxentius, she went to the Emperor and rebuked him for his cruelty. The Emperor summoned 50 of the best pagan philosophers and orators to dispute with her, hoping that they would refute her pro-Christian arguments, but Catherine won the debate. Several of her adversaries, conquered by her eloquence, declared themselves Christians and were at once put to death.

The emperor gave orders to subject Catherine to terrible tortures and then throw her in prison. Her legend tells that during the confinement she was fed daily by a dove from heaven, and Christ also visited her, encouraging her to fight bravely, and promised her the crown of everlasting glory. Angels tended her wounds with salve.

During her imprisonment more than 200 people came to see her, including Maxentius' wife, Valeria Maximilla; all converted to Christianity and were subsequently martyred. Upon the failure of Maxentius to make Catherine yield by way of torture, he tried to win her over by proposing marriage. Catherine refused, declaring that her spouse was Jesus Christ, to whom she had consecrated her virginity.

The furious emperor condemned Catherine to death on a spiked breaking wheel, but at her touch it shattered. Maxentius ordered her to be beheaded. Catherine ordered the execution to commence. As per her legend, a milk-like substance rather than blood flowed from her neck.

In the 6th century, the Eastern Emperor Justinian had established what is now Saint Catherine's Monastery in Egypt, which had been originally built encircling the purported burning bush seen by Moses. Countless people make the pilgrimage to the monastery to receive miracle healing from Catherine.