主显节前夕，又称第十二夜，是基督教节日的一个分支，指1月5日。那一天晚上是十二天圣诞季的最后一夜，之后就是圣诞节后第十二日（1月6日）的主显节。主显节纪念的是东方三博士对耶稣基督的朝拜。主显节过后就是狂欢季的开始，一直持续到忏悔星期二（即四旬节的前一天）。有些地区如美国路易斯安娜州的新奥尔良，则把1月6日晚上的狂欢节称为“第十二夜”。

在一些地区，第十二夜的庆祝活动包括传统食品如国王蛋糕、果子奶油蛋糕。

莎士比亚的戏剧《第十二夜》原来就是为庆祝主显节前夕而作的。

Twelfth Night is a festival in some branches of Christianity marking the coming of the Epiphany. Different traditions mark the date of Twelfth Night on either 5 January or 6 January; the Church of England, Mother Church of the Anglican Communion, celebrates Twelfth Night on the 5th and "refers to the night before Epiphany, the day when the nativity story tells us that the wise men visited the infant Jesus". In Western Church traditions the Twelfth Night concludes the Twelve Days of Christmas, although in others the Twelfth Night can precede the Twelfth Day. Bruce Forbes wrote that " "In 567 the Council of Tours proclaimed that the entire period between Christmas and Epiphany should be considered part of the celebration, creating what became known as the twelve days of Christmas, or what the English called Christmastide. On the last of the twelve days, called Twelfth Night, various cultures developed a wide range of additional special festivities. The variation extends even to the issue of how to count the days. If Christmas Day is the first of the twelve days, then Twelfth Night would be on January 5, the eve of Epiphany. If December 26, the day after Christmas, is the first day, then Twelfth Night falls on January 6, the evening of Epiphany itself."