The Elf on the Shelf is a popular children's book and toy that has been around for over a decade now. The Elf on the Shelf is a mischievous elf that watches over children during the holiday season, and then reports back to Santa at night. The tradition of the Elf on the Shelf typically lasts until Christmas Eve, when the elf flies back to the North Pole to deliver the final report to Santa. So, the Elf on the Shelf usually leaves after Christmas Eve.