Stir-up Sunday is an informal term in the Anglican Church for the last Sunday before the season of Advent.
The term comes from the opening words of the collect for the day in the Book of Common Prayer of 1549 and later collect "Excita, quæsumus"):
Stir up, we beseech Thee, O Lord, the wills of Thy faithful people; that they, plenteously bringing forth the fruit of good works, may of Thee be plenteously rewarded; through Jesus Christ our Lord. Amen.
Through an association of ideas, the day subsequently became connected, especially in England, with the preparation of Christmas puddings in readiness for Christmas.
In recent years, many have adopted the practice of observing this last Sunday before Advent as Christ the King Sunday (sometimes under the name the Reign of Christ Sunday). Popular attachment to the Stir up collect has, however, caused it to be retained (in contemporary language) in the liturgies of several Churches.