AltaVista is a web search engine owned by Yahoo!. AltaVista was once one of the most popular search engines but its popularity declined with the rise of Google. In 2010, Yahoo! announced that it plans to discontinue the site.
AltaVista was created by researchers at Digital Equipment Corporation's Western Research Laboratory who were trying to provide services to make finding files on the public network easier. Although there is some dispute about who was responsible for the original idea, two key participants were Louis Monier, who wrote the crawler, and Michael Burrows, who wrote the indexer. The name AltaVista was chosen in relation to the surroundings of their company at Palo Alto. AltaVista was publicly launched as an internet search engine on 15 December 1995 at altavista.digital.com.

At launch, the service had two innovations which set it ahead of the other search engines; It used a fast, multi-threaded crawler (Scooter) which could cover many more Web pages than were believed to exist at the time and an efficient search running back-end on advanced hardware. As of 1998, it used 20 multi-processor machines using DEC's 64-bit Alpha processor. Together, the back-end machines had 130 GB of RAM and 500 GB of hard disk space, and received 13 million queries per day. This made AltaVista the first searchable, full-text database of a large part of the World Wide Web. The distinguishing feature of AltaVista was its minimalistic interface compared with other search engines of the time; a feature which was lost when it became a portal, but was regained when it refocused its efforts on its search function.

AltaVista's site was an immediate success. Traffic increased steadily from 300,000 hits on the first day to more than 80 million hits a day two years later. The ability to search the web, and AltaVista's service in particular, became the subject of numerous articles and even some books. AltaVista itself became one of the top destinations on the web, and by 1997 would earn US$50 million in sponsorship revenue.