St Stephen's Day, celebrated in Vatican City as well as many other countries across the world, is a public holiday that falls on 26th December. This holiday holds religious significance as it commemorates the life of Saint Stephen, a Christian deacon in Jerusalem who was stoned to death for blasphemy, making him the first Christian martyr. Due to its occurrence immediately after Christmas, it's often intertwined with Christmas celebrations in many cultures.

In Vatican City, a city-state enclaved within Rome, Italy, the Pope leads the congregation in the celebration of St Stephen's Day. As the city-state that serves as the spiritual and governmental headquarters of the Roman Catholic Church, the holiday is marked with great reverence and ceremony. This celebration could include giving sermons about the life and martyrdom of Stephen, special prayers, singing hymnals and readings of the biblical passage 'Acts of the Apostles 6:8-10; 7:54-60', which recounts St. Stephen’s martyrdom.

The day is not just of religious significance, but also has a cultural component. St. Stephen's Day in Vatican City might also include performances of sacred music, processions, and potentially even reenactments of the saint's martyrdom. Light plays an essential role in the celebrations as St. Stephen is often portrayed with stones and the shining light of God, marking the first Christian martyr’s full commitment to his faith. Through these traditions, St. Stephen's Day serves as a profound reflection on the theme of martyrdom in Christian faith.