Sacha Baron Cohen Denies Rebel Wilson 'A**hole' Claim in Memoir

7:11 AM PT -- A rep for Sacha Baron Cohen tells TMZ … "While we appreciate the importance of speaking out, these demonstrably false claims are directly contradicted by extensive detailed evidence, including contemporaneous documents, film footage, and eyewitness accounts from those present before, during and after the production of The Brothers Grimsby."

Rebel Wilson claims Sacha Baron Cohen is trying to make her keep his name out of her book as an "a**hole" in showbiz -- and she suggests he's trying to muzzle her.

The actress teased that one of the chapters in her forthcoming memoir, 'Rebel Rising,' will name a douchebag in Hollywood that she says she had a bad experience with -- teasing the prospect of identifying this alleged jerk nearly 2 weeks ago ahead of her book's release.

Welp, late Sunday ... she got ahead of her own deadline and called out this person directly on social media -- claiming Sacha's the guy, with some other choice words for him as well.

Rebel writes, "I will not be bullied or silenced by high priced lawyers or PR crisis managers. The "asshole" that I am talking about in ONE CHAPTER of my book is: Sacha Baron Cohen."

The accusation follows a video Rebel posted on March 15, in which she somewhat detailed her run-in with Sacha -- explaining she'd been told by some early in her career that they had a zero-tolerance policy on "assholes" in the industry ... saying SBC kickstarted her own.

The two of them starred in 2016's "The Brothers Grimsby" -- with Sacha playing the lead and Rebel playing a key supporting role. Other costars include Sacha's wife, Isla Fisher, Mark Strong, Lex Shrapnel, Rory Keenan, Tamsin Egerton and others. Louis Leterrier directed.

Rebel hasn't elaborated on what exactly she believes Sacha did to gain this rep in her mind -- but in any case ... she says she's dedicated multiple pages to the guy, and the whole story will be out soon enough for all to peruse.

The memoir is out April 2 -- it's being distributed by Simon & Schuster.

We've reached out to Sacha's team for comment ... so far, no word back.