In the mid-noughties, a couple of business students at USC discussed the lack of post-release support in the games industry and the Asian distribution model of releasing games for free with in-game purchases. This conversation led to the founding of Riot Games.

Riot Games was founded in September 2006 in Santa Monica, California by University of Southern California roommates Brandon Beck and Marc Merrill.

A small team developed a working prototype of League of Legends in just four months and presented it at GDC 2007 to secure further investment funds.

In 2008, Riot Games struck a deal with Tencent Holdings to launch League of Legends in China, marking a significant partnership between the two companies.

On July 14, 2009, Riot Games announced that League of Legends will be free with 'no catch'.

On October 7, 2009, Riot Games announced the launch of League of Legends, a highly popular multiplayer online battle arena game.

Riot Games released League of Legends as a free-to-play game on October 27, 2009, and actively engaged with players to make adjustments based on their feedback.

On May 10, 2010, Riot Games announced that they would take over distribution and operation of their game in Europe and relocated their European headquarters to new offices in Dublin.

An article in Bloomberg Businessweek from June 27, 2011, discussed the convergence of virtual and real worlds, possibly referencing the impact of online gaming communities like League of Legends.

On May 1, 2012, Riot Games announced its Season 2 Championship with a $2,000,000 prize pool.

By 2013, League of Legends was the most-played multiplayer PC game in the world.

By 2014, League of Legends had 67 million monthly active users, more than double its 2012 total, making it a massively popular game.

Tencent bought the remaining 7 percent of Riot Games on December 16, 2015.

In March 2016, Riot Games acquired Radiant Entertainment, another developer who was working on Rising Thunder and Stonehearth at the time.

Riot Games released the tabletop strategy game Mechs vs. Minions in October 2016.

On October 13, 2017, Beck and Merrill announced that they were returning their focus to developing games, aiming to create new experiences for video game and esports players.

As of May 2018, Riot Games employed 2,500 people, operating 24 offices around the world.

In the first half of 2018, Kotaku reported on allegations of discrimination against female employees at Riot Games, including overlooked ideas, grooming for senior positions, and a 'bro culture' working environment. The report also mentioned receiving inappropriate images and a list detailing which female employees senior staff members would sleep with.

Riot's CEO announced the suspension of the company's COO, Scott Gelb, for two months without pay for workplace misconduct. The company also updated its values on the website to reflect the 'bro culture' mentioned in the Kotaku report.

The game was announced by Riot Games and entered its first preview on October 15, 2019, coinciding with the tenth anniversary of League of Legends.

In January 2020, Riot Games announced the formation of Riot Tabletop, a division dedicated to producing tabletop games. The first game released under this division was Tellstones: King's Gambit in 2020.

In February 2020, as a result of the state's findings that the terms of the settlement should have been valued higher, the class withdrew the proposed US$10 million settlement and brought on new lawyers who had been involved in prior lawsuits related to the Me Too movement.

In April 2020, Riot Games acquired Hypixel Studios after investing in the studio for eighteen months. This acquisition was aimed at supporting the development and publishing of Hytale, a voxel-based sandbox game.

Valorant was officially launched in June 2020, introducing the game to a wider audience.

Riot announced a planned partnership with the developing city of Neom in Saudi Arabia in July 2020 but canceled the partnership shortly after due to criticism over Saudi Arabia's human rights record and the violent attempts to evict the Howeitat tribe from the area during the city's construction.

Jason Bunge was hired as Riot Games' chief marketing officer in October 2020.

Riot organized the First Strike esports tournament for Valorant in November 2020, which received positive feedback from critics and players.

Hextech Mayhem is an event in the game League of Legends, featuring a new game mode and exclusive in-game rewards. It is themed around the Hextech universe and offers players a unique gameplay experience.

Riot and Laurent were sued by Laurent's former assistant in January 2021 on sexual discrimination charges, which included inappropriate language and labor mistreatment.

In March 2021, Alienware ended its partnership with Riot a year earlier than their contract term due to the ongoing litigation over sexual harassment allegations.

In August 2021, Riot agreed to a new settlement with the DEFH and employees of $100 million, with $80 million going to the impacted employees. The settlement was approved in July 2022, compensating 1,548 female employees between $2,500 and $40,000 each.

In October 2021, the company bought Kanga, a services firm involved in 'fan hubs', merchandising, and content aggregation.

Riot Games collaborated with French animation studio Fortiche to release the animated series, Arcane, in November 2021. The series received positive critical reception and was made available worldwide on Netflix and in China by parent company Tencent.

After Russia launched an invasion of Ukraine in February 2022, Riot Games donated proceeds from in-game items to humanitarian relief organizations operating in Ukraine, totaling $5.4 million.

In March 2022, Riot Games announced its investment in Fortiche, resulting in the appointment of its chief content officer and director of corporate development to Fortiche's board of directors.

The first RBC in Dublin, Ireland, opened in July 2022, equipped with an IP-based infrastructure, six studios, and preserving the nightclub's disco ball. This marked a milestone in Riot Games' efforts to enhance the production quality of its esports events.

In October 2022, Riot Games acquired Wargaming Sydney, a subsidiary of Wargaming, and renamed it Riot Sydney. This acquisition excluded rights to the BigWorld technology and its publishing arm.

Following the bankruptcy of FTX in November 2022, Riot Games began seeking legal methods to terminate the FTX contract. This event signified a significant challenge in Riot Games' business partnerships and financial strategies.

Riot's upcoming 2D assist-based fighting game set in the world of Runeterra, featuring champions from League of Legends. The game aims to provide fast-paced combat with room for creativity and self-expression.

In January 2024, Riot Games announced the layoff of 530 employees, about 11% of its workforce, and the sunset of the Riot Forge effort and Riot Esports Network. The decision was stated to be a necessity for maintaining a long-term focus for players.