The "Living for Love" hitmaker is currently fighting for custody of her 15-year-old son Rocco against her former husband Guy Ritchie.
Captioning a sweet letter from her supporters, she wrote: "Thanks soooooo much for this! It means a lot to me! One word of kindness it can save me! (sic)"
The message, signed from "Your Rebel Hearts", pays tribute
to their idol for "rescuing [them] every single day".
It reads: "M, we'll keep it simple. WE ARE HERE. As we have always been, and always will. Whatever things you're going through right now (We are aware that we don't know everything), no one else than your true fans keep their minds and hearts with you on them.
"There's a lot of comments saying this. But we did this to make it official and do it all of us, the fans together. WE LOVE YOU, FOREVER. Your Rebel Hearts.