Dota 2 is a free-to-play multiplayer online battle arena (MOBA) video game or massively multiplayer online role-playing game (MMORPG) developed and published by Valve Corporation.

The game initially used the original source game engine until it was ported over to Source 2 in 2015, making it the first game to use it. Despite some criticism going towards its steep learning curve and complexity, the game was praised for its rewarding gameplay, production quality, and faithfulness to its predecessor. The popularity of the game has led to official merchandise being produced for it, including apparel, accessories, and toys, as well as promotional tie-ins to other games and media.

Dota 2 has a widespread and active competitive scene, with teams from across the world playing professionally in various leagues and tournaments. Premium Dota 2 tournaments often have prize pools totaling millions of US dollars, the highest of any eSport. The largest of them is known as The International, which is produced annually by Valve and held at the KeyArena in Seattle. Valve also sponsors smaller, but more frequently held tournaments known as the Majors, which lead up to the International every year. For larger tournaments, media coverage is done by a selection of on-site staff who provide commentary and analysis for the ongoing matches, similar to traditional sporting events. Broadcasts of professional Dota 2 matches are streamed live over the internet, and sometimes simulcast on television networks, with peak viewership numbers in the millions. Dota 2 is an RTS-styled competitive team game with RPG elements. Two competing teams of five players (Radiant and Dire). The main objective in Dota 2 is to destroy the enemy Ancient inside their stronghold. These strongholds are protected by multiple towers down 3 lanes. Instead of building armies of units like in classical RTS games, each player controls a single Hero, a strategically-powerful unit with unique abilities and characteristics which can be improved over the course of the game. Experience is earned when nearby creeps and heroes die, and once collecting enough experience, the hero gains a level, which increases the hero's stats, and at most levels the hero gains a skill point which can be spent to unlock or upgrade one of the hero's abilities. Alongside a hero's fixed abilities, each hero has 6 inventory slots which can be filled with Items which provide various benefits and abilities. To purchase these items, Gold is gained passively over time, by killing creeps, by killing enemy heroes and by destroying buildings. Dota 2 has an heavy emphasis on tactics and team co-ordination, and a deep amount of strategy focused on building up strength as fast as possible, optimal itemization, and selecting what order to upgrade your hero's spells.