The musician, who was the bassist and vocalist in the group in the 70s and featured on their second and third albums, has sadly passed away.
A statement on Gordon's Facebook page reads: “It is with great sadness we announce the passing of Gordon, a great musician and a wonderful person who will be sadly missed by so many."
At the time of writing, Gordon's cause of death is unknown.
The musician was a school friend of King Crimson's guitarist and founding member, Robert Fripp, and also played in his bands League Of Gentlemen and Fleur de Lys.
Robert asked Gordon to join King Crimson after vocalist Greg Lake quit.
He went on to provide the bass and added his vocals to ‘Cadence and Cascade’ from their second album ‘In the Wake of Poisedon’, and across their third LP ‘Lizard’.
However, Gordon left the group after their third album due to creative differences.
King Crimson have paid tribute to their former bandmate and said the work he did during his time in the band is "much admired".
They wrote: “Gordon Haskell’s Facebook page is reporting that Gordon has died.
“His time in KC wasn’t a particularly happy part of his long career but his work on In The Wake Of Poseidon and in particular, Lizard is much admired in the Crimson community.”
Following his time in King Crimson, Gordon went on to have a successful solo career, with 'How Wonderful You Are' from 2001's 'Look Out' reaching number two in the UK, with Robbie Williams and Nicole Kidman's cover of 'Somethin' Stupid' claiming the top spot.
Gordon released 13 solo albums during his career, his most recent, 'The Cat Whos Got The Cream', came out in January this year.