League of Legends was formally announced on October 7, 2008.
It was in a closed beta from April 10, 2009, to October 22, 2009. 17 champions were available upon the launch of the alpha in April 2009: Alistar, Annie, Ashe, Fiddlesticks, Jax, Kayle, Master Yi, Morgana, Nunu, Ryze, Sion, Sivir, Soraka, Teemo, Tristana, Twisted Fate, and Warwick.
On 27, October 2009, League of Legends was released on PC and macOS to be a free online multiplayer game by Riot Games.
In 2010 Riot staged an April Fool's Joke where they introduced a fake new champion, "Urf the Manatee." After a large amount of enthusiasm from the game's player base, Riot decided to donate the proceeds made from selling in-game skins to the Save the Manatee Club, a national non-profit organization striving to save and raise awareness of manatees.
In Europe, Riot Games initially signed an international licensing partnership with GOA, the video games department of Orange's Content Division, and Europe's largest gaming portal. On October 13, 2009, GOA and Riot announced that they would start channeling server access for players located in Europe to GOA's dedicated servers. This partnership did not last; on May 10, 2010, Riot Games announced that they would take over the distribution and operation of the game in Europe. To do so, Riot Games established a European HQ in Dublin.
By 2011 players were starting an average of ten games of League of Legends every second with 15 million registered players to the servers according to Riot. Other important milestones included over one million games of LoL being played every day, with 1.4 million players logging daily to spend 3.7 million cumulative hours. The heavy player count, especially on days the game was being patched, led to server instability. Brandon Beck stated in an interview that server stability was one of their "key priorities" as the game grew faster than anticipated were working to improve the player experience.
The Season 1 Championship was held at DreamHack in Sweden, in June 2011 and had US$100,000 in prizes. The European team Fnatic defeated teams from Europe, the USA, and Southeast Asia to win the tournament and received US$50,000 in prize money. Over 1.6 million viewers watched the streamed broadcast of the event, with a peak of over 210,000 simultaneous viewers in one semi-final match.
After a series of network issues during the Season 2 World Playoffs that led to several matches being delayed, Riot revealed on October 13, 2012, that a special LAN-based client had been quickly developed, designed for use in tournament environments where the effects of lag and other network issues can be detrimental to the proper organization of an event. The LAN client was deployed for the first time during the first quarter-final and semi-final matches played following the rescheduled matches and were in use during the finals. On October 13, 2012, the Taipei Assassins (TPA) of Taiwan triumphed over Azubu Frost of South Korea in the Finals of Season 2 World Championship with a score of 3 to 1 and claimed the $1 million in prize money.
On July 11, 2013, Riot Games announced that the United States Citizenship and Immigration Services recognized League of Legends pro players as professional athletes and that the P visa application process would be more simplified for them. These changes allowed professional players to stay in the United States for up to five years. Despite these reforms, there have still been a number of visa problems that have occurred for players in the LCS and other LoL tournaments entering the United States.
In October 2013, Korean team SK Telecom T1 and Chinese team Royal Club competed at the Season 3 World Championship at the Staples Center in Los Angeles. SK Telecom T1 won the grand prize of $1 million, and Royal Club received $250,000.
In October 2015, SK Telecom T1 became the first-ever two-time World Champion when they defeated fellow Korean team KOO Tigers with a score of 3 to 1 in the best-of-five finals in Berlin, Germany.
Changes for the 2016 season included adding a loot system that allows players to acquire content such as full character and skin unlocks. It was the first time the game had ever awarded character skins for free. Riot also announced that in an effort to punish negative behavior, some players would be ineligible for these rewards due to past negative behavior.
SK Telecom T1 repeated their feat in October 2016, defeating fellow Korean team Samsung Galaxy 3-2 in the Season 6 World Championship.
The 2017 tournament, hosted in China, also grew a considerable prize pool of roughly $5 million. Riot once again in 2017 decided to take profits from skin sales to increase the prize pool. The initial pool was $2 million and 250 thousand dollars, however, Championship Ashe, the new championship skin for 2017, sold well. 25% of Championship Ashe and ward sales allowed the prize pool to grow. 24 teams battled until only SK TelecomT1 and Samsung Galaxy were the last 2 teams standing. Samsung Galaxy won dominantly with a 3-0 against SK TelecomT1 in The National Stadium(Birds Nest) in Beijing, allowing Samsung Galaxy to take home the 1st place prize pool of $1.8 million.
In 2018 League of Legends got a new PvE mode called Odyssey.
The 2018 tournament, hosted in South Korea, was the chance for Riot to continue to exceed expectations. Riot, as was tradition now, took 12.5% of Championship Kha'Zix and ward sales to increase the prize pool. The other 12.5% was decided to be divided among all participating teams of the tournament. The prize pool rose compared from last year's $5 million to roughly $6.5 million. The finals were held in The Munhak Stadium in Incheon, where Fnatic faced off against Invictus Gaming. Invictus Gaming would go on to 3-0 sweep Fnatic to take home the 1st place prize pool of $2.4 million. Invictus Gaming would make history for themselves, for this was not only their first World Championship win, but also the first Chinese team to win an international tournament.
In 2019 Riot Games celebrated the 10th anniversary of League of Legends. During an online stream, Riot announced a variety of new game projects based on the world of League of Legends, as well as in-game gifts which players would receive.
The 2019 tournament, hosted in Europe, lead to another clean sweep match. The newer team, created in 2017, FunPlus Phoenix faced off and took a 3-0 victory from the well known European team, G2 Esports in AccorHotels Arena in Paris, France. The statistics for all sources of income besides the guaranteed prize of $2 million and 250 thousand dollars are unavailable, however, FunPlus Phoenix did win roughly 800 thousand dollars from that part of the prize pool.
In 2019, League of Legends won the eSports game of the year award from The Game Awards 2019 event.