This gift might be a “fake” — believe it or not.

Kim Kardashian rocked generations of fans when she stepped out on the Met Gala red carpet wearing one of Marilyn Monroe’s most iconic looks.

The dress was a loaner from Ripley’s Believe it Or Not! Museum in Orlando, Florida, which reportedly also surprised the 41-year-old reality TV star with what they claimed to be a lock of the legendary bombshell’s platinum hair.

However, Monroe historian Scott Fortner claims to have debunked Ripley’s story, and may have the receipt to prove it.

“News Alert: Marilyn Monroe Hair Gifted to Kardashian by Ripley’s is Fake,” Fortner declared on Instagram. On Friday, the collector re-shared Ripley’s clip of Kardashian accepting her gift, followed by a screenshot from the museum’s website, and what Fortner claims to be a photo of a 1962 hair salon receipt — putting the hair-loom’s origins into question.

Fortner is said to keep the world’s largest private collection of Monroe’s property and archives, according to his website TheMarilynMonroeCollection.com, where he also shared a blog post billing Kardashian’s Monroe lock as “fake.”

According to Ripley’s, the “lock was clipped by her hairstylist Robert Champion just prior to her Madison Square Garden performance,” when she famously crooned “Happy Birthday” to President John F. Kennedy.

The museum notes that the lock from the starlet’s signature blonde bob was “authenticated by John Reznikoff, one of the most respected and trusted experts in the field of hair collecting.”

But Fortner has alleged that hairstylist Champion never touched Monroe’s hair on that infamous night.

“Paul Fraser Collectibles sold the hair in 2019,” he explained in the caption of his post. “Their description for the lot: ‘Just hours before her performance, Monroe visited her personal hairdresser Robert Champion at the Coiffures Americana Beauty Salon, housed within the luxury department store Bergdorf Goodman on Fifth Avenue.’ ”

He continued, “One could assume the hair given to KK was part of this lot of hair that was cut by Robert Champion ‘just prior to her MSG performance.’ “

“News Flash: Robert Champion did not cut and style Marilyn’s hair for the JFK gala. It was actually the one and only ‘Mr. Kenneth’ (Kenneth Battelle) who had the honors,” Fortner testified on social media.

“Battelle is responsible for Marilyn’s famous hairstyle from that night, as documented by a receipt from Lilly Dache Beauty Salon … The receipt, dated May 25, 1962, lists a ‘Hair Dress’ and references May 18 and 19, 1962. May 19th was the date of the Kennedy gala. The bottom the receipt reads, ‘Kenneth Services at home Fri + Saturday.’ Marilyn paid $150 for the service,” the expert explained.

Ripley’s, Reznikoff and Fortner did not respond to The Post’s request for comment.