Christmas is an annual festival commemorating the birth of Jesus Christ, observed primarily on December 25 as a religious and cultural celebration among billions of people around the world. A feast central to the liturgical year in Christianity, it follows the season of Advent (which begins four Sundays before) or the Nativity Fast, and initiates the season of Christmastide, which historically in the West lasts twelve days and culminates on Twelfth Night. Christmas Day is a public holiday in many countries, is celebrated religiously by a majority of Christians, as well as culturally by many non-Christians, and forms an integral part of the holiday season surrounding it. The traditional Christmas narrative recounted in the New Testament, known as the Nativity of Jesus, says that Jesus was born in Bethlehem, in accordance with messianic prophecies. When Joseph and Mary arrived in the city, the inn had no room, and so they were offered a stable where the Christ Child was soon born, with angels proclaiming this news to shepherds, who then spread the word.

The customs associated with Christmas in various countries have a mix of pre-Christian, Christian, and secular themes and origins. Popular holiday traditions include gift giving; completing an Advent calendar or Advent wreath; Christmas music and caroling; watching Christmas movies; viewing a Nativity play; an exchange of Christmas cards; attending church services; a special meal; and displaying various Christmas decorations, including Christmas trees, Christmas lights, nativity scenes, garlands, wreaths, mistletoe, and holly. Additionally, several related and often interchangeable figures, known as Santa Claus, Father Christmas, Saint Nicholas, and Christkind, are associated with bringing gifts to children during the Christmas season and have their own body of traditions and lore. Because gift-giving and many other aspects of the Christmas festival involve heightened economic activity, the holiday has become a significant event and a key sales period for retailers and businesses. Over the past few centuries, Christmas has had a steadily growing economic effect in many regions of the world.