The December 2021 New Year's Smash was the second New Year's Smash professional wrestling television special produced by All Elite Wrestling (AEW). It took place on December 29, 2021, at Daily's Place in Jacksonville, Florida. The two-part event was broadcast on TNT as special episodes of AEW's weekly television programs, Wednesday Night Dynamite and Friday Night Rampage. Dynamite aired live while Rampage aired on tape delay on December 31. It was the second New Year's Smash event to be held in 2021, after the first took place in January. The Dynamite broadcast was the show's final episode on TNT as Dynamite moved to TNT's sister channel TBS on January 5, 2022.

AEW New Year's Smash is a professional wrestling television special produced by All Elite Wrestling (AEW). Established by the promotion in 2021, the event is held annually around New Year's as a two-part event. The original January 2021 event aired as two back-to-back special episodes of AEW's flagship program, Wednesday Night Dynamite, while the second event, which aired in December 2021, occurred during the same week, first as an episode of Dynamite, then as a special episode of Friday Night Rampage, with future events retaining this format. The Dynamite broadcast for the second event was notable for being the final Dynamite to air on TNT before the show moved to TNT's sister channel TBS; Rampage remained on TNT.