The tennis players had been together for around two years but Grigor, 24, confirmed in an interview this week that they'd called time on their relationship.
According to Sky News, he said: "Our paths split. We experienced wonderful moments together. I wish her much happiness and success in life and in tennis."
The tennis stars have always kept their relationship away from the limelight, although they were dating as recently as June because Grigor spoke about her in an interview with The Telegraph that month.
Discussing how he'd marked Maria's 28th birthday, he said he'd sent roses to Stuttgart where she'd been playing in a tennis tournament.
"Her favourite, mine as well. Sometimes I just go crazy and send her hundreds – 500 is the most I've ever sent at once."
Try Reveal 's digital edition On iPhone & iPad. Subscribe now!