Chad Johnson is turning to the FBI for help ... after a sex tape featuring the former NFL star leaked onto the Internet, TMZ has learned.
The footage shows Chad in a Florida hotel room ... doing the dirty with a tatted-up female.
Sources close to Chad tell TMZ, he's furious ... and believes the video was hacked from his phone -- much like Scarlett Johansson's nude photos. So, like Scarlett, he's contacted the FBI to help hunt down the culprit.
TMZ broke the story ... Chad admits the tape is real but insists he's not the one who leaked it. He says it was shot more than 3 years ago.
We're told Chad's still waiting for a response from the Bureau -- but he's not sitting around ... he's contacted his lawyer (who deals specifically with cyber crimes) to put together a cease-and-desist letter to get the footage yanked from the web.