Catherine of Alexandria, also spelled Katherine (Greek: Αίκατερίνη) is, 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. More than 1,100 years after Catherine's martyrdom, Joan of Arc identified her as one of the saints who appeared to and counselled her.

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".