Sid Wilson is officially out as Slipknot's DJ and keyboardist ... TMZ has learned.

A source close to the band and with direct knowledge tells TMZ ... Sid was notified late Friday afternoon that he's been permanently kicked out of the band.

It's currently unclear what led to him getting the boot.

This comes on the heels of his split from Kelly Osbourne back in March. They quietly called off their engagement, but our sources said at the time that there's still a chance they could get back together.

Sid was one of the group's nine original members -- having been with them since 1999 -- and the latest OG to leave.

Craig Jones and Chris Fehn are both no longer with the band. Joey Jordison passed away in his sleep in 2021 ... and Paul Gray died from a drug overdose in 2010.