Gamergate or GamerGate (GG) was a loosely organized misogynistic online harassment campaign motivated by a right-wing backlash against feminism, diversity, and progressivism in video game culture. It was conducted using the hashtag "#Gamergate" primarily in 2014 and 2015. Gamergate targeted women in the video game industry, most notably feminist media critic Anita Sarkeesian and video game developers Zoë Quinn and Brianna Wu.

Gamergate began with an August 2014 blog entry called "The Zoe Post" by Quinn's ex-boyfriend, which falsely insinuated that Quinn had received a favorable review because of Quinn's sexual relationship with a games journalist. The blog post was spread to 4chan, where many users had previously disparaged Quinn's work. This led to a campaign of harassment against Quinn, coordinated through anonymous message boards such as 4chan, 8chan, and Reddit. The harassment campaign expanded to target Sarkeesian, Wu, and others who defended Quinn, and included doxing, rape threats, and death threats.

Gamergate proponents ("Gamergaters") claimed to be promoting ethics in video game journalism and protecting the "gamer" identity in opposition to "political correctness" and the perceived influence of feminism and so-called social justice warriors on video game culture. Proponents alleged there was a conspiracy between journalists and video game developers to focus on progressive social issues such as gender equality and sexism. Such claims have been widely dismissed as trivial, baseless, or unrelated to actual issues of ethics in gaming and journalism. Several commentators in the mass media dismissed the ethics complaints as a deliberate cover for the ongoing harassment of Quinn and other women. Gamergaters frequently denied any such harassment took place, falsely claiming it to be manufactured by the victims.

Gamergate has been described as a culture war over cultural diversification, artistic recognition, feminism in video games, social criticism in video games, and the social identity of gamers. Supporters stated that it was a social movement. However, as a movement Gamergate had no clearly defined goals, coherent message, or official leaders, making it difficult to define. Gamergate led figures both inside and outside the gaming industry to focus on methods of addressing online harassment, ways to minimize harm, and prevent similar events. Gamergate has been viewed as contributing to the alt-right and other right-wing movements.

In 2013, Zoë Quinn, an independent game developer, released Depression Quest, a text-focused game designed to convey the experience of depression through a series of fictional scenarios, based in part on Quinn's own experience with the illness. The game received positive reviews in the gaming media and from mental health professionals, but faced backlash online from gamers who disliked its departure from typical game formats emphasizing violence and skill and who opposed "political" intrusions into gamer culture. Quinn was subjected to several months of harassment after its release, including rape and death threats. Quinn documented the harassment they received and spoke openly to the media about it, which led to more pronounced abuse against them such as the posting of their home address online. They cancelled future public appearances and ultimately fled their house out of fear for their safety.

The controversies and events that would come to be known as Gamergate began in August 2014 as a personal attack on Quinn, incited by a blog post by Quinn's former boyfriend, Eron Gjoni. Called "The Zoe Post", it was a lengthy, detailed account of their relationship and breakup that included copies of personal chat logs, emails, and text messages. The blog falsely implied that Quinn received a favorable review of Depression Quest in exchange for a sexual relationship with Nathan Grayson, a reporter for the gaming websites Kotaku and Rock Paper Shotgun. Gjoni later said that he had "no evidence" of a sexual conflict of interest on Quinn's part. Grayson never actually reviewed any of Quinn's games, and his only Kotaku article mentioning them was published before their relationship began. Nonetheless, as reported by The Daily Dot, gamers online used Gjoni's blog to accuse Quinn, without evidence, of trading sex for professional advancement. A link to the blog was posted to 4chan, where many users had previously been highly critical of Depression Quest, which led to renewed attacks on Quinn.

After Gjoni's blog post, Quinn and their family were subjected to a virulent and often misogynistic harassment campaign. Online attackers of Quinn at first used the label "Quinnspiracy", later adopting the hashtag "#Gamergate" after it was coined by the actor Adam Baldwin on August 27, 2014, whose nearly 190,000 Twitter followers helped the spread of the hashtag. Right-wing journalist Milo Yiannopoulos popularized the hashtag on Breitbart News, becoming one of the most prominent voices of Gamergate and the antifeminist movement more broadly. Harassment of Gamergate targets was coordinated via IRC, spreading rapidly over imageboards and forums like 4chan and Reddit.

Less than four months after Gamergate began, Quinn's record of threats they had received had grown 1,000-fold. At a conference Quinn said, "I used to go to game events and feel like I was going home ... Now it's just like ... are any of the people I'm currently in the room with ones that said they wanted to beat me to death?" One anonymous 4chan user threatened to give them "a crippling injury that's never going to fully heal". Commentators both inside and outside the video game industry condemned the attacks against Quinn. The attacks included doxing (researching and broadcasting personally identifiable information about an individual) and hacking of their Tumblr, Dropbox, and Skype accounts; they were again subjected to rape and death threats. Quinn again fled their home to stay with friends. Quinn wrote that "the Internet spent the last month spreading my personal information around, sending me threats, hacking anyone suspected of being friends with me, calling my dad and telling him I'm a whore, sending nude photos of me to colleagues, and basically giving me the 'burn the witch' treatment".