Memory Alpha (often abbreviated to MA) is a wiki that is an encyclopedic reference for topics related to the Star Trek fictional universe. Conceived by Harry Doddema and Dan Carlson in September 2003 and officially launched on December 5 of that year, it uses the wiki model and is hosted by Wikia, Inc. on the MediaWiki software. According to Jane Klobas, the site is a large and vibrant resource. Memory Alpha contains over 31,000 articles in its English edition alone as of July 2010^[update], making it one of the largest wiki projects. The site is also available in several other languages, including Bulgarian, Chinese, Czech, Dutch, Esperanto, French, German, Italian, Japanese, Polish, Portuguese, Russian, Serbian, Spanish and Swedish.

Memory Alpha aims to create a comprehensive database for all fans, but was not conceived as a wiki. Two concerns spurred its creation: many Star Trek references of the time were incomplete, and the most promising would shut down regularly, like the site TrekPulse, which closed inexplicably in late 2005 to be reborn the next year as TrekCore. Doddema and Carlson christened their project Memory Alpha, after the Federation's largest information archive, from the original series episode "The Lights of Zetar".