Madonna's family is in mourning ... because her stepmother has died.
The "Like a Virgin" singer's stepmom, Joan Ciccone, died Tuesday after a battle with a very aggressive cancer ... according to her obituary.
Joan was Madonna's housekeeper growing up in Michigan ... and a couple years after Madonna's mother died at age 30 -- also from cancer -- Joan married Madonna's father, Silvio Ciccone.
Joan and Silvio had two children together, Madonna's half-sister Jennifer and her half-brother Mario.
She has appeared in a couple of documentaries about Madonna ... including "I'm Going To Tell You a Secret" and a TV episode of "Biography."
Like Madonna, Joan was born and raised in Michigan ... and with a bunch of kids at home with Silvio, she opened a daycare and ran it for two decades.
Joan and Madonna's father started their own wine business in Michigan, founding and operating Ciccone Vineyard and Winery. Joan planted the vines, harvested the grapes and cooked for tasting room events. She was also passionate about fashion and antiques.
Madonna's stepmom is being remembered by loved ones for her "enthusiasm, joy and love."
We reached out to Madonna's camp ... so far no word back.
Joan was 81.
RIP