Wikipedia Day is celebrated on January 15 of each year since 2001, on the anniversary of the birth of Wikipedia.
Wikipedia Day has been celebrated, both online and offline, for several years. There is a tradition of diverse local meetups and wiki-events for Wikipedia Day around January every year, and on a larger scale Wikipedia Day unconferences have been held in several localities since 2010.
As 2001 is technically the birthday of English Wikipedia, other editions have sometimes celebrated their particular languages on their own founding days.
Landmark anniversaries have been observed by the Wikimedia Foundation and the global movement for the 10th and 15th anniversaries, with a centralized campaign to promote more local events, and will likely be again for the 20th anniversary.
- 2011: Wikipedia 10
- 2016: Wikipedia 15
- 2021: Wikipedia 20
- Wikipedia Day on English Wikipedia (and other language editions) for historical notes and local organizing year by year
- WQ/Retro for a 2005 retrospective of Wikipedia and flashbacks to Wikipedia Days past
- List of Wikimedia birthdays