Dota 2 is an action real-time strategy game developed and published by Valve Corporation. It's a stand-alone sequel to the WarCraft III custom map Defense of the Ancients: All-Stars (DotA:All-stars for short, or simply DotA). Development of Dota 2 began in 2009, when the current developer of the DotA mod, IceFrog, was hired by Valve as lead designer. Dota 2 was released as a free-to-play title on Steam, and is a direct competitor to League of Legends and the less popular game Heroes of Newerth .

Dota 2 prize pools can reach over $1 million through the use of crowd-funding. The International is Valve's annual tournament for Dota 2, the largest in Dota 2 esports, where the best Dota 2 players compete for a crowd-funded, multi-million dollar cash prize pool. Prior to releasing the Compendium for The International 2015 (abbreviated to TI5), Valve announced plans for the Dota Major Championships which encompasses The International and three Valve-sponsored events leading up to it. The TI5 prize pool ended up being over $18 million, with the prize money continuing to grow year-after-year.

On June 12, 2015, Valve announced that Dota 2 would be ported over to the Source 2 engine, in an opt-in beta update titled "Dota 2 Reborn". The update included a new user interface framework design, ability for custom game modes, and replacing the original Source engine with Source 2, officially making Dota 2 the first Source 2 game. The beta was released to the public on June 17, 2015, and fully replaced the original game client on September 9, 2015.