Stir-up Sunday is an informal term in the Anglican Church for the last Sunday before the season of Advent, officially termed "The Twenty-fifth Sunday after Trinity".

The term comes from the opening words of the collect for the day in the Book of Common Prayer of 1549 and later:

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.

A rubric in the Book of Common Prayer of 1662 referring to this day as "The Sunday next before Advent" reinforced the significance of this day as forming part of the preparation for the festival of Advent.