The Mortal Kombat tournament was originally thought to be a solely human conception, until later retcons revealed it to be universal among the series' featured Realms, created by the Elder Gods as a way for other realms to defend themselves against Outworld after it grew too powerful.
A realm may declare Mortal Kombat on another realm if they wish to invade it and conquer it. Once one party declares Mortal Kombat, the other party may not refuse. A tournament ensues, where the combatants will be knocked out until the reigning champion does battle with the challenger. Once defeated, a single Tournament victory is added for the realm. Once that realm earns ten Tournament victories in a row, they earn the right to invade the losing realm. This is the only 'legal' way for a realm to invade another, and any violation of this rule is seen as treason against the Elder Gods. The reigning champion will have their aging suspended by the Elder Gods until the next tournament.
* 1000-500 years before Mortal Kombat: The first known Mortal Kombat tournament, created when sorcerer Shang Tsung, under orders by Outworld emperor Shao Kahn, took control of an Earthrealm Shaolin tournament in a bid to upset the furies and invade Earth. The first tournament, Shang Tsung was defeated by Great Kung Lao.
* 500-0 years before Mortal Kombat: The Great Kung Lao held his position as Grand Champion for only one generation, after which his title - and his life - was taken by Shang Tsung's newest warrior, Goro, who held the title for another nine victories.
* Mortal Kombat: Liu Kang, who is a young monk, defeats Goro, thus breaking his winning streak and preventing Outworld's invasion of Earth. Shang Tsung challenges Liu Kang to a battle but is defeated while trying to salvage something from his champion's loss. As such, he is forced to relinquish his hold on the tournament and flee back to Outworld.
* Mortal Kombat II: A false tournament proposed by Shang Tsung to Shao Kahn, to lure Earth's warriors to Outworld by kidnapping Sonya, where Kahn's forces would have a distinct advantage. It also posed as a distraction away from Kahn's revival of his wife, Queen Sindel on Earth, which would force a merger of the realms regardless of the false tournament's outcome. Liu Kang gains victory. After this, no official Mortal Kombat tournament is held, with all future storylines following all-out war between the realms.
* Mortal Kombat: Deadly Alliance: Although the main storyline doesn't involve a tournament for the main characters, at this time, there was a tournament going on; one set up by Shang Tsung and his partner, the necromancer Quan Chi to give the Outworld native Li Mei a chance to free her people, who were currently enslaved by the two sorcerers in order to build a temple over a Soulnado, a means of which they could achieve their goals of ultimate power and immortality. This tournament has not been expressly stated as a Mortal Kombat tournament, and it is highly debatable among fans whether or not it can be called such, but regardless, it was as fake as the one set up in MK2, with the sorcerers having no intention of keeping their word, regardless of the outcome.