Amy Winehouse -- Singer Gets Second Billing ... On Her GRAVESTONE

Amy Winehouse's gravestone has been unveiled in London ... and even though she was a worldwide superstar, she didn't get top billing on her final marquee.

Amy is buried alongside her grandmother Cynthia Levy, who passed away 5 years before the 27-year-old singer ... and the two share a gravestone, with Cynthia's name on top.

The stone reads, "In loving memory of Cynthia Levy ... and her beloved granddaughter Amy Jade Winehouse."

The inscription continues, "Forever in the hearts of their devoted family."

Winehouse died on July 23, 2011 after a hardcore alcohol binge.

R.I.P.