Jamie came to the 'Tonight Show' host's defense with a series of comments on Jimmy's IG post where he did actually say he was sorry for his 'SNL' impression of Chris Rock.

Jamie said Jimmy "ain't got to apologize for s**t" and called him a great comedian who did an incredible impersonation.

But, what's interesting is ... Jamie says what Jimmy did is NOT blackface. As we reported ... Jimmy did a mea culpa Tuesday after the clip from the year 2000 resurfaced on social media with the hashtag, #jimmyfallonisoverparty.

Jimmy said, "I made a terrible decision to do an impersonation of Chris Rock while in blackface. There is no excuse for this." He added, "I am very sorry for making this unquestionably offensive decision and thank all of you for holding me accountable."

But, for anyone trying to cancel Jimmy ... Jamie's NOT having it. He went on to say in defense of his bud, "Some of y’all didn’t even see the sketch… relax and laugh! it's Other muuuuuuphuckas out there that really don’t care bout ya… use that energy for them!!! But leave my mans alone."