The Mid-Season Invitational (MSI) is an annual League of Legends international tournament hosted by Riot Games in the middle of years, since 2015.

[2][3] In 2015 and 2016, the event featured the Spring Split champions of the five major competitive League of Legends regional leagues (LEC, LCS, LCK, LMS, LPL), as well as a wildcard team from a region determined by the International Wildcard Invitational, held a few weeks beforehand.

The best Wildcard region receives a direct spot in the World Championship's Group Stage for that year for their Summer Split champion.

In line with last years iteration, 5 teams qualified to participate at the Mid-Season Invitational after winning the Spring Split within their own regional leagues, while a team from the Wildcard regions qualified by winning the Mid-Season International Wildcard Invitational (IWCI).

The 2017 Mid-Season Invitation was held from 28 April to 21 May 2017, in 2 cities across Brazil: São Paulo (play in) and Rio de Janeiro (groups and knockout stage).

[13] The final was played on 21 May 2017, hosted in the Jeunesse Arena, between defending champions SK Telecom T1, from South Korea's League of Legends Champions Korea, and G2 Esports, from the European League of Legends Championship Series, with SK Telecom T1 retaining the championship 3–1, becoming the first team to win back-to-back Mid-Season Invitationals.

[25] Due to the COVID-19 pandemic, Riot Games cancelled the event, replacing it with the Mid-Season Streamathon, a series of international competitions and exhibition matches from multiple regions.

[28] GAM Esports, from the Vietnam Championship Series, was unable to attend the event due to travel restrictions related to the COVID-19 pandemic.

Royal Never Give Up won the championship 3–2, becoming the second team after T1 (formerly SK Telecom T1) to win two Mid-Season Invitationals.

Thirteen teams from nine regions qualified for the event as champions of their regional Spring splits, excluding North America (LCS), EMEA (Europe, the Middle East and Africa), Korea (LCK), and China (LPL), who each had two teams participate in the tournament.

[40] The format for the event differed to the previous editions, with the introduction of a play-in stage, consisting of eight teams who are split into two double elimination brackets.

[46] Twelve teams from eight regions qualified for the event, with Japan's LJL merging under the Pacific Championship Series (PCS).

[52] On 8 January 2025, Riot Games announced that the 2026 and 2027 editions of MSI would be held in South Korea and Europe respectively.