Invisibility is an ability that can be used to hide or conceal one's physical complexion.

• Graham Garrett, also known as the Chameleon, was an assassin, with the ability to make himself invisible. Clark's x-ray vision can't detect him. 
• Wes Keenan had genetic strands from Graham Garrett used to give him invisibility as part of Project Ares.

• Jeff Palmer, with the aid of a cream that he created, Jeff was able to render himself invisible to the naked eyes.

• John Jones can turn himself invisible, allowing him to sneak up on people. (Static)

• Kenny Cavanaugh is a meteor freak who can turn himself invisible. (Paterfamilias)

• Dawn Mills was a Smallville High student who could turn herself invisible. (See No Evil)

Appearances

• Season 1: Shimmer
• See No Evil
• Smallville (comic book): Paterfamilias
• Season 5: Fade
• Season 6: Prototype

Trivia

• Clark Kent could not see through Graham Garrett's invisibility with his X-ray vision, but Clark could see through Jeff Palmer. Therefore, this is another proof of the invisibility Lex Luthor used in Project Ares for Wes Keenan was Graham's, because Clark couldn't see through Wes Keenan with his X-ray visison.

In the Comics

Martian Manhunter is extremely talented in rendering himself invisible, by causing the bio-polymers in his body to lose their ability to reflect light, making him invisible to normal light and human sight. With excessive concentration, he can render himself completely invisible along the electromagnetic spectrum, including the infrared and the ultraviolet ranges of the spectrum. This invisibility does not affect every other sense and he could still be detected by touch.