The model and actress, 34, made the shock announcement on Twitter on Friday night (26 September).
Just last week, Kelly and bodybuilder David enjoyed a sun-drenched holiday on the Greek Island of Mykonos. But things clearly soured after their return.
Making the most of their holiday together, Kelly and David posted lots of loved-up snaps on social media - but now Kelly has removed all photos of David from her Instagram account.
Kelly took to Twitter to update her fans on her relationship status.
She wrote: "It's a sad day but I wanted to share with you that David and I are no longer engaged. I love and respect him and wish him all the best."
So far, former Gladiator David has not mentioned the split on social media.
The pair confirmed their engagement in March after a whirlwind 11-week relationship.
It's a sad Day but I wanted to share with you that David and I are no longer engaged. I love and respect him and wish him all the best.— Kelly Brook (@IAMKELLYBROOK) September 26, 2014
In August, David took part in Celebrity Big Brother, but was the first to be voted out of the house.
Kelly is currently in LA working on upcoming American sitcom One Big Happy, which will air on major US network NBC. It co-stars 24 actress Elisha Cuthbert and is being produced by Ellen DeGeneres.
The plot revolves around a man who decides to have a baby with his lesbian best friend, only to then meet Kelly's character and really confuse things.
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