Google Groups is a service from Google that provides discussion groups for people sharing common interests. Until February 2024, the Groups service also provided a gateway to Usenet newsgroups, both reading and posting to them, via a shared user interface. In addition to accessing Google Groups, registered users can also set up mailing list archives for e-mail lists that are hosted elsewhere.

Google Groups became operational in February 2001, following Google's acquisition of Deja's Usenet archive. Deja News had been operational since March 1995.

Google Groups allows any user to freely conduct and access threaded discussions, via either a web interface or e-mail. There are at least two kinds of discussion groups: forums specific to Google Groups (like mailing lists) and Usenet groups, accessible by NNTP, for which Google Groups acts as gateway and unofficial archive. The Google Groups archive of Usenet newsgroup postings dates back to 1981.

Google Groups no longer supports posting or viewing new Usenet content since February 22, 2024. Existing archives remain available.

The Deja News Research Service was an archive of messages posted to Usenet discussion groups, started in March 1995 by Steve Madere in Austin, Texas. Its search engine capabilities won the service acclaim, generated controversy, and significantly changed the perceived nature of online discussion. This archive was acquired by Google in 2001.

While archives of Usenet discussions had been kept for as long as the medium existed, Deja News offered a novel combination of features. It was available to the public, provided a simple World Wide Web user interface, allowed searches across all archived newsgroups, returned immediate results, and retained messages indefinitely. The search facilities transformed Usenet from a loosely organized and ephemeral communication tool into a valued information repository. The archive's relative permanence, combined with the ability to search messages by author, raised concerns about privacy and confirmed often-repeated past admonishments that posters should be cautious in discussing themselves and others.

While Madere was initially reluctant to remove archived material, protests from users and legal pressure led to the introduction of "nuking", a method for posters to permanently remove their own messages from search results. It already supported the use of an "X-No-Archive" message header, which if present would cause an article to be omitted from the archive. This did not prevent others from quoting the material in a later message and causing it to be stored. Copyright holders were also allowed to have material removed from the archive. According to Humphrey Marr of Deja News, copyright actions most frequently came from the Church of Scientology.

The capability to "nuke" postings was kept open for many years but later removed without explanation under Google's tenure. Google also mistakenly restored previously "nuked" messages at one point, angering many users. "Nukes" that were in effect at the time when Google removed the possibility are still honored, however. Since May 2014, European users can request to have search results for their name from Google Groups, including their Usenet archive, delinked under the right to be forgotten law. As of 2015, Google Groups was one of the ten most delinked sites. If Google does not grant a delinking, Europeans can appeal to their local data protection agencies.