Sonic & Knuckles
The game's special cartridge
Developer(s)	Sonic Team
Publisher(s)	Sega
Director(s)	Hirokazu Yasuhara
Producer(s)	Yuji Naka
Designer(s)	Takashi Iizuka
Composer(s)	Howard Drossin Tatsuyuki Maeda
Series	Sonic the Hedgehog
Platform(s)	GameCube Linux macOS Microsoft Windows PlayStation 2 PlayStation 3 Sega Genesis Sega Saturn Wii Xbox Xbox 360
Genre(s)	Platform
Mode(s)	Single-player

Sonic & Knuckles is the fifth video game in the Sonic the Hedgehog series.^[a] It was made by Sonic Team and published by Sega for the Sega Genesis in 1994. It is the second part of Sonic the Hedgehog 3. In the game, players are able to play as Sonic the Hedgehog and Knuckles the Echidna.

A Sonic 2 or Sonic 3 cartridge can be inserted into it to unlock new modes for those games. This is called "Lock-on Technology".

Continuing right after the ending of Sonic 3, Sonic and Tails discover the Super Emeralds in Mushroom Hill Zone. They are more powerful versions of the Chaos Emeralds. Sonic and Tails head to Hidden Palace Zone and fight Knuckles. After Sonic and Tails win, the three see Robotnik stealing the Master Emerald and betraying Knuckles. Knuckles switches sides and joins Sonic and Tails. Using the last of his energy, Knuckles leads them to Sky Sanctuary Zone so that they can climb onto the now-repaired Death Egg and confront Robotnik. If the player has collected all of the Super Emeralds in the special stages, Hyper Sonic^[b] can fight Robotnik's final weapon in outer space. After destroying it, Sonic returns the Master Emerald and leaves with Tails. Knuckles, as the emeralds' guardian, stays on the island.

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