Keith Richards marked the occasion by posting a pic of them, saying, "Mick, Wishing you a Happy Birthday! Love, Keith."

Ronnie Wood piled on ... "Wishing @mickjagger a very happy birthday!"

It's remarkable ... Mick and co. have been together for 6 decades, and they're still a group. There have been a million ups and downs ... feuds between Mick and Keith, tell-all books ... but in the end, they are brothers joined at the hip, and there's a lot of love between them.

The band 86'd its No Filter Tour back in March ... this because of the coronavirus. They did, however, perform a virtual concert for "One World: Together at Home Concert," and it was fabulous.

Mick's had some health issues recently ... last year he underwent heart valve replacement surgery, but it only sidelined him for a short period of time ... he was back on stage doing his thing.

Happy Birthday, Mick!!!