Christmas () is an annual holiday that celebrates the birth of Jesus. It refers to both the day commemorating the birth, and also the Christmastide season which that day inaugurates, concluding with the Feast of the Epiphany. The date of the celebration is traditional, and is not considered to be Jesus' actual date of birth. Christmas festivities often combine the observation of the Nativity with various cultural customs, many of which have been influenced by earlier winter festivals. Although nominally a Christian holiday, it is also observed as a cultural holiday by many non-Christians.

In most places around the world, Christmas Day is celebrated on December 25. Christmas Eve is the preceding day, December 24. In Germany and some other countries, the main Christmas celebrations commence on the evening of the 24th.

The day following Christmas Day, December 26, is called Boxing Day in the United Kingdom and many countries of the Commonwealth, and called St. Stephen's Day or the Feast of Saint Stephen in Catholic countries.

The Armenian Apostolic Church observes Christmas on January 6. Eastern Orthodox Churches that still use the Julian Calendar celebrate Christmas on the Julian version of 25 December, which is January 7 on the more widely used Gregorian calendar, because the two calendars are now 13 days apart.

The prominence of Christmas Day increased gradually after Charlemagne was crowned on Christmas Day in 800. Around the 12th century, the remnants of the former Saturnalian traditions of the Romans were transferred to the Twelve Days of Christmas (25 December ? 5 January). Christmas during the Middle Ages was a public festival, incorporating ivy, holly, and other evergreens, as well as gift-giving.

Modern traditions have come to include the display of Nativity scenes, holly and Christmas trees, the exchange of gifts and cards, and the arrival of Father Christmas or Santa Claus on Christmas Eve or Christmas morning. Popular Christmas themes include the promotion of goodwill and peace.