Mortal Kombat: Deception is a fighting game in the Mortal Kombat series. Deception was developed and published by Midway for the PlayStation 2 and Xbox in October 2004. A GameCube version was published in February 2005.

Mortal Kombat: Deception precedes Shaolin Monks (in release date only) and follows Deadly Alliance. Deception was released in two versions for the Playstation 2 and Xbox; the regular version for both systems, a "Premium Pack" for Playstation 2, and "Kollector's Edition" for Xbox; both of which added a metal trading card and a bonus disc containing a history of Mortal Kombat, several video biographies of characters, and an "arcade perfect" version of the original Mortal Kombat. The game is known as Mortal Kombat Mystification in France. It is considered one of the more nostalgiac entries by many fans, as it marked the return of many characters that haven't been seen in many installments, as well as many remade classic stages.

In the final events of Deadly Alliance, Raiden's warriors (Kitana, Kung Lao, Jax Briggs, Johnny Cage, and Sonya Blade) lay down during their battle against the Tarkatan warriors and ultimately, the Deadly Alliance itself (Shang Tsung and Quan Chi). The Elder Gods had advised Raiden not to interfere, but he defied their wishes; alone he challenged the alliance of Tsung and Quan Chi inside Shang Tsung's palace, in Mortal Kombat. Raiden fought spectacularly, dealing powerful blows to the sorcerers and almost killing Quan Chi at one point. Shang Tsung then cheats, and absorbs a soul from the soulnado. He uses this to strike down Raiden, and the Deadly Alliance then combine their magic and take the thunder God down.

With Raiden defeated, the Deadly Alliance turned on each other, with Tsung wanting Quan Chi's amulet. The Deadly Alliance was no more and Tsung found himself facing his one time partner Quan Chi. Despite Tsung's efforts, Quan Chi proved too much for him. Quan Chi struck Tsung to the ground, snapped his arm, then strangled Tsung, gagging blood out of his mouth. When Quan Chi stood alone, a hulking form entered the tomb, and the mummies of the Dragon King's army turned to kneel. In disbelief, Quan Chi looked in shock and in great horror... Onaga, the Dragon King, had returned.

Quan Chi knew what the Dragon King had come for: his amulet. Quan Chi unleashed his powers on Onaga, and as Tsung awoke, they combined their powers and used their projectile streams. Onaga began to run toward them, just as Raiden stalked forward and stood by the sorcerers. The three pooled their efforts together, and struck the Dragon King. Momentarily staggered, Onaga begins to sprint forward now. Realising that it was not working, Raiden starts an incantation, while thunder and light flies around him. Onaga comes closer and closer, as Quan Chi finally notices Raidens energy fluctuations. "What are you doing?!" he snapped desperately. Raiden's intentions then become clear, as he unleashes all his Godly essence in a colossal explosion. The blast snuffs out the soulnado, kills both members of the Deadly Alliance, and devastates the surrounding area. But it had little effect on Onaga, who has now recovered his amulet...

Onaga now seeks to use six artifacts called Kamidogu, literally "Tool of God" from the Japanese words Kami (God) and Dogu (Tool), to fuse the realms into the One Being, resulting in the destruction of everything therein. Those fighters not killed in the battle against the Deadly Alliance (Li Mei, Raiden, Scorpion, Sub-Zero, Kenshi and Bo' Rai Cho) must now stand against him and his supporters. These include the Tarkatan horde (led by Baraka) and their former allies, who were resurrected by Onaga and are under his control.

In the story explored in Konquest mode, a young man named Shujinko is deceived (hence the game's title) into spending his life collecting the Kamidogu for Onaga, who uses the guise of an emissary of the Elder Gods named Damashi. This is prior to Onaga's resurrection in the body of Reptile. Onaga only reveals his identity and intentions after Shujinko has gathered all the Kamidogu. Shujinko, led to believe he was working for the greater good, joins the others opposing Onaga.