CM Punk is sure Elon Musk was giving a Nazi salute at that Donald Trump inauguration event back in January ... and the WWE Superstar is adamant there's no amount of "gaslighting" the billionaire can do to sway his opinion.

The 46-year-old wrestler went in on the Tesla honcho during an appearance on this week's "The Ringer Wrestling Show" ... insisting Musk gave a "Sieg Heil" while speaking to a pro-Trump crowd at Capital One Arena on Jan. 20.

Musk, of course, has stated the gesture was nothing more than an impassioned wave -- pointing out in an X post that plenty of politicians have made similar moves -- but Punk told the guys on the pod he's not buying it.

"We saw what you did," Punk said. "Don't gaslight me. I'm not as f***ing stupid as you are. I know what you did so I know what you are. Now I know where you stand, and this is where I stand."

The conversation came about as the show's hosts asked how he'd advise younger WWE talent on how to address politics publicly. Punk stated he figured his company doesn't want "us to be outwardly political" -- though he said he'd always make his opinions known ... even if it upset the left, the right, and/or, clearly, Musk.

"It's just a f***ing strange, ugly world out there," he said. "The only thing I can do is be true to myself and implement and be a voice for myself and my family and my community, and then the world."

He went on to dig at Elon further during his chat on the pod ... when he gave his thoughts on X trolls who have called his employer "a MAGA company."

"Well, you're on Lord Elon Musk's f***ing Twitter saying stupid s***," he said. "Like, shut the f*** up."