'Mr. Big Stuff' Singer Jean Knight Dead at 80

8:23 PM PT -- TMZ has confirmed Jean passed away Wednesday, and we've confirmed the authenticity of the press release circulating on social media ... which we're told comes from her family. Her publicist also tells us Jean died from natural causes.

Her family released a statement, which notes her long storied career which started at JetStream Records and eventually jumped to Stax Records ... and all the tunes she produced in between, ending with her starting her own label (Comstar).

The statement ends ... "Jean Knight's legacy is not just a musical one; it is a testament to the enduring love between an artist, her hometown, and the fans who adored her. As we bid farewell to this iconic soulstress, New Orleans and her global fan base join together in gratitude for the indelible mark she left on the world." The family requests privacy at this time.

Jean Knight -- most famous for her hit 'Mr. Big Stuff' -- has died ... this according to reports.

An unattributed press release purporting to be the soul singer and New Orleans native's obituary is making the rounds online -- and if it's to be believed ... it says JK passed away last Wednesday, although the circumstances surrounding her death are unclear for now.

Knight's 1971 song is easily her biggest claim to fame, but it's a huge contribution to music and pop culture. 'Mr. Big Stuff' not only performed incredibly well on the charts when it came out -- including five weeks at #1 on the Billboard Soul Singles chart, and peaking at No. 2 on the Billboard Hot 100 -- but it ended up being featured in numerous films and TV shows.

Just a handful of series that used 'MBS' ... 'Family Guy,' 'black-ish,' 'The Marvelous Mrs. Maisel,' 'Everwood' and 'The Deuce' -- just to name a few. On the movie front, it got played in Will Ferrell's 'Semi-Pro.' Beyond that ... the track got remixed/sampled a ton over the years.

Some of that notable acts who flipped this gem ... Heavy D & The Boyz, Eazy-E, TLC, Queen Latifah, Everclear, Girl Talk, Beastie Boys and John Legend. 'Mr. Big Stuff' had also been covered a handful of times ... famously by Precious Metal, Lyn Collins and many others.

Jean had recorded lots of other songs throughout her career ... but none ever reached the success of 'Big Stuff.' Some of her other notable singles ... "My Toot Toot," "You Think You're Hot Stuff," "Carry On," "Helping Man," "Do Me," "Jesse Joe (You Got to Go)" ... and more.

She was 80.

RIP