An Advent calendar is a special calendar used to count the days of Advent in anticipation of Christmas.

Since the date of the First Sunday of Advent varies, falling between November 27 and December 3 inclusive, many Advent calendars, especially those that are reusable, often begin on December 1, although those that are produced for a specific year often include the last few days of November that are part of the liturgical season.

The Advent calendar was first used by German Lutherans in the 19th and 20th centuries.