Justin Timberlake once told Michael Jackson to get lost … only to realize he’d just cursed out the King of Pop himself.

JT shared the wild story on Complex’s “Re-Rank” … revealing Michael called him out of the blue about *NSYNC’s hit “Gone,” which Justin had originally written for MJ.

Justin said he pitched several songs to Michael, but when “Gone” got rejected, he handed it over to *NSYNC … and it landed on the group’s 2001 album “Celebrity.”

Then his phone rang from an unfamiliar number … and when the caller greeted him with “Hi, Apple Head,” JT assumed it was a prank and let a few choice words fly.

Turns out, it was Michael … sending Justin into full apology mode. As JT put it, “I just cursed Michael Jackson out.”

But MJ wasn’t calling to complain … he actually loved “Gone” and wanted to rerecord it as a duet with Justin, even though *NSYNC had already released it.

Justin suggested including the whole group, but Michael wasn’t having it … he wanted just the two of them.

And in a surprising twist, JT turned him down … saying he couldn’t abandon the fellas, even for the King of Pop.