Saint Mark's Day, or the Feast of Saint Mark, commemorates Mark the Evangelist and takes place on April 25.

Mark the Evangelist (Latin: Marcus; Greek: Μᾶρκος, romanized: Mârkos; Aramaic: ܡܪܩܘܣ, Marqōs; Hebrew:מארק), also known as Saint Mark, is the person who is traditionally ascribed to be the author of the Gospel of Mark. According to Church tradition, Mark founded the episcopal see of Alexandria, which was one of the five most important sees of early Christianity. His feast day is celebrated on April 25, and his symbol is the winged lion.

The Feast of St Mark is observed on April 25 by the Catholic and Eastern Orthodox Churches. For those Churches still using the Julian Calendar, April 25 according to it aligns with May 8 on the Gregorian Calendar until the year 2099. The Coptic Orthodox Church observes the Feast of St Mark on Parmouti 30 according to the Coptic Calendar which always aligns with April 25 on the Julian Calendar or May 8 on the Gregorian Calendar.

Where John Mark is distinguished from Mark the Evangelist, John Mark is celebrated on September 27 (as in the Roman Martyrology) and Mark the Evangelist on April 25.

Mark is remembered in the Church of England and in much of the Anglican Communion, with a Festival on 25 April.