The Sonic the Hedgehog 25th Anniversary was a celebration that started in 2016 of twenty-five years since the start of the Sonic the Hedgehog series with the release of Sonic the Hedgehog in 1991. It was preceeded by the twentieth anniversary and followed by the thirtieth anniversary.
Variations of the twenty fifth anniversary were celebrated for other characters until 2019, including Tails' anniversary for Sonic the Hedgehog 2, Amy and Metal Sonic's anniversary for Sonic the Hedgehog CD, and Knuckles' anniversary for Sonic the Hedgehog 3.
- Mario & Sonic at the Rio 2016 Olympic Games
- LEGO Dimensions
- Sonic Boom: Fire & Ice
- Sonic Dash (Classic Sonic and Green Hill Zone event)
- Sonic Mania
- Sonic Forces
- Toys by Tomy
- Sonic the Hedgehog × Sanrio toys by Toynami
- Classic Sonic diorama by First 4 Figures
- Classic Sonic statue by Sega Prize!
- Blind-box toys and a statue by Kidrobot
- Plush toys by Build-A-Bear Workshop
- Various merchandise from Sega Shop
- Sonic the Hedgehog 25th Anniversary Art Book
- Sonic 25th Cafe Selection
- Sonic the Hedgehog 25th Anniversary Selection
- Sonic 25th Anniversary Party
- Sonic 25th Anniversary Party at Joypolis
- Sonic 25th Anniversary Cafe at Sweets Paradise
- The Sonic the Hedgehog 25th Anniversary Collection
- 25th Anniversary theme for Nintendo 3DS
- As of the thirtieth anniversary, the twenty-fifth anniversary logo is so far the only anniversary logo where the number is not red.
- 「ソニック・ザ・ヘッジホッグ」生誕25周年を記念した「ソニック25周年カフェ」がオープン！ 10/1(土)～11/13(日)の期間限定でスイーツパラダイス上野ABAB店にコラボメニュー＆グッズが登場！ (Japanese). Sega (13 September 2016). Archived from the original on 24 October 2020.
- 25 years of Sonic the Hedgehog. Castle Fine Art. Archived from the original on 29 October 2020.