"The split is amicable and the pair continue to have nothing but the utmost respect for one another," Osbourne's rep said in a statement. "Kelly is looking forward to a new year full of fresh beginnings. No further comments will be provided by all parties and we request privacy, decorum and space from the press but don't expect it."
Osbourne seemed to address the break up in a tweet on Wednesday.
"Its all about perception sometimes the bad things that happen in life aren't really bad at all especially when you learn something from it!" she wrote.
Osbourne and Mosshart confirmed their engagement in an interview last July.
"We'd dated for a year and knew we wanted to be together," Osbourne said at the time. "Matthew has broken down every one of my walls. There's nothing I wouldn't do in front of him."
"I knew she was 'the one' pretty early on," Mosshart said.