On Dec. 3, 1968, Elvis Presley emerged from eight years of shallow Hollywood mediocrity to reclaim his crown as the unmistakable King of Rock ‘n’ Roll.

An hourlong NBC special, “Elvis,” taped the previous June in Burbank, featured a slim, black-leather-clad Presley, 33, in a pared-down, informal, acoustic concert before a small studio audience. It was shot with handheld cameras by director Steve Binder and caught Presley at the peak of his powers as he joyously sang and bantered with musicians including Scotty Moore and DJ Fontana — the guitarist and drummer who’d backed Presley on most of his early hits and were reuniting with him after many years.

“Elvis,” also called “The ’68 Comeback Special,” was the granddaddy of “MTV Unplugged” — 20 years before the fact.

It’s the subject of a new Paramount+ documentary, “Reinventing Elvis: The ’68 Comeback,” which takes viewers behind the curtain of the original NBC telecast through the eyes of Binder, 90, who shares candid, emotional, behind-the-scenes stories of working with Presley and with his notoriously iron-fisted, sketchy manager, Col. Tom Parker (identified here as “The Villain”), who’d relegated Elvis to a string of laughably bad movies throughout the 1960s to keep the gravy train rolling along.

“Reinventing Elvis: The ’68 Comeback” is produced by Spencer Proffer (“The Day The Music Died: The Story of Don McLean’s ‘American Pie’”) and directed by John Scheinfeld (“The U.S. vs. John Lennon”), with Binder and Bruce Gilmer executive-producing.

“Steve [Binder] was the only guy that Elvis would truly listen to,” Proffer told The Post. “This is Steve’s documentary, and Elvis is the vehicle by which we were able to tell Steve’s story about [the ’68 special] and standing up to Tom Parker,” said Proffer, who’s known Binder since 1968. “Steve could not be manipulated … [NBC] wanted him to be the guy to bring Elvis forward … and [‘The 68 Comeback Special’] is what he did on his terms, in his own way.”

Binder wrote the coffee table book “Elvis ’68 Comeback: The Story Behind the Special,” published last year; the Paramount+ documentary was a chance for him “to bring Elvis back to life visually,” Proffer said.

“Steve is the only living authority on the making of that special — he directed it, he produced it and it was his brainchild,” he said. “This is not a documentary on Elvis. This is a documentary about bringing Elvis back from where Col. Parker flushed his career away with the bad movies he made after the Army. Steve saw a side of Elvis that he spotlighted in the context of the special, using handheld cameras to shoot in the round.

“This is Steve’s documentary and Elvis is the vehicle by which we were able to tell Steve’s story.”

The Dutch-born, manipulative Parker (he wasn’t a colonel, was possibly a felon, and was played by Tom Hanks in Baz Lurhmann’s 2022 movie “Elvis”) envisioned the NBC telecast as a schmaltzy Christmas special in which Presley would croon a slate of holiday songs a la Perry Como.

But Binder had other ideas.

As viewers will see in “Reinventing Elvis,” that included pairing Presley with Moore, Fontana, Charlie Hodge, Alan Fortas, and Lance LeGault and inviting a small studio audience to their mini-concert, much to Parker’s chagrin (he tried to sabotage Binder’s plan).

“It was Steve who said that, when he heard Elvis jamming backstage, he thought, instinctively, that Elvis would be more comfortable around his cronies,” Proffer said. “So he flew them in on his measly [network] budget and put them in the round and Parker didn’t want that. So he took the tickets and flushed them away and Steve went to [fast food place] Bob’s Big Boy and a local radio station and all the people you see [watching the concert] were people recruited 12 hours before it was shot.”

Proffer said it’s easy to see why the “68 Comeback Special” still resonates 55 years later (Presley died on Aug. 16, 1977, at the age of 42).

“It’s organic purity because Elvis was organic to who he was,” Proffer said. “He was a true rocker, a true mover and shaker of music vocally and musically and Steve’s job was to be the magnet to pull that out and to capture it with handheld cameras.

“This is who Elvis was — not the guy singing in B-movies,” Proffer said. “You couldn’t fake that — you couldn’t cut it, could do it with digital tricks, could do it via AI. You couldn’t do anything but capture it and that’s what Steve Binder did.

“The public at large who think Elvis is yesterday’s news, who remember him as that fat guy from Las Vegas in jumpsuits, that’s not who he was,” Proffer said. “He was the cool guy playing guitar with his guys and singing in a black leather suit.

“That’s what Steve’s vision was — and that’s what this documentary is about.”