Which Sonic the Hedgehog game introudced Knuckles the Echidna?

The Sonic the Hedgehog game that introduced Knuckles the Echidna is Sonic the Hedgehog 3. Released in 1994, this game marked the first appearance of the red echidna as a playable character. Knuckles served as a rival to Sonic, initially being deceived by Dr. Robotnik into believing that Sonic was a threat. However, as the game progressed, Knuckles ultimately realized the truth and teamed up with Sonic to defeat their common enemy. Ever since then, Knuckles has become one of the beloved characters in the Sonic franchise.