The Nymphomaniac actor opened up about the incident during a bizarre interview with Dazed Digital, conducted over email before he and the reporter sat staring at each other in silence for an hour.
"One woman came with her boyfriend, who was outside the door when this happened," the Daytime Emmy winner wrote in his email interview.
"[She] whipped my legs for 10 minutes and then stripped my clothing and proceeded to rape me.
"There were hundreds of people in line when she walked out with dishevelled hair and smudged lipstick. It was no good, not just for me but her man as well."
He explained Mia Goth, his girlfriend of two years, was among the hundreds waiting for a one-on-one with him when the woman left his room.
"It was Valentine's Day and I was living in the gallery for the duration [February 11-16] of the event," LaBeouf wrote.
"We were separated for five days, no communication.
"So it really hurt her as well, as I guess the news of it travelled through the line.
"When she came in she asked for an explanation, and I couldn't speak, so we both sat with this unexplained trauma silently. It was painful."
Actor Shia LaBeouf. Photo / Getty Images
LaBeouf also vented his frustration at gallery patrons who would "come in, take my [paper] bag off, pop off a selfie, and bounce."
"Some would hold my hand and cry with me, some would tell me to 'figure it out' or to 'be a man.' I've never experienced love like that; empathy, humanity."
In the wide-reaching interview, LaBeouf confessed that he longed for the kind of family he saw in the 1990 flick Home Alone.
"I always had a f****d up view on masculinity," he admitted.
"My father [Jeffrey] was a gun nut like Hemingway. He was also a junkie and a bully, mainly to prove he wasn't effeminate, even though he was a painter and a poet, a mime, and a storyteller."
After corresponding with British reporter Aimee Cliff for two weeks online, the pair donned GoPros and sat together silently in LaBeouf's London hotel room last month.
The hour-long 'metamodernist encounter' was mostly a chance for the two to stare awkwardly with intermittent giggles.
INTERVIEW from Rönkkö / Turner on Vimeo.
#IAMSORRY was the culmination of several bizarre incidents - belligerent outbursts, plagiarism, and public martyrdom involving paper-bag masks marked: "I am not famous anymore."
In June, the Transformers star was arrested for criminal trespass, disorderly conduct, and harassment at a Broadway production of Cabaret.
According to TMZ, the judge gave Shia a "thumbs-up" after he brought a progress report detailing his outpatient alcohol rehab to Manhattan Criminal Court on Tuesday.
He's due in court again March when he completes his treatment.
LaBeouf just ranked #21 on GQ's listicle of 30 least influential people of 2014 alongside Woody Allen, Robin Thicke, and Zach Braff.
The Charlie Countryman actor shaved his head for his role as former U.S. Marine Gabriel Drummer in the post-apocalyptic thriller Man Down.
In it, Shia - who joined the US National Guard this year - reunited with his Guide to Recognizing Your Saints director Dito Montiel.
Gary Oldman, Kate Mara, and Jai Courtney also appear in Man Down - due out October 30.
LaBeouf can currently be seen as tank soldier Boyd Swan in the WWII flick Fury with Brad Pitt, Scott Eastwood, and Michael Peña.
- Daily Mail
