"She was my musical soulmate and like a sister to me," Ronson told his Twitter followers. "This is one of the saddest days of my life."
Ronson -- who's set to marry French model Josephine de La Baume on September 3 -- worked with Winehouse on her Back to Black album in 2007. The following year, the album won five Grammy Awards (including Producer of the Year).
Back to Black's backing band, Sharon Jones & the Dap-Kings -- along with the entire Daptone Records family -- tell Us Weekly in a statement: "We are very sad to have lost Amy Winehouse today. She was one of a kind and we were fortunate to have had the chance to make music with her. She was always gracious and a pleasure to work with in the studio and on the road. She brought a lot of people joy with her voice and her irreverent personality. It is a tragedy that she was taken from us so soon when she had much more music to give."