The TV chef, 51, married 30-year-old Anne-Marie - who is 21 years his junior - in a romantic ceremony at Hever Castle, Kent, on Saturday afternoon.
A whole host of famous faces turned out to celebrate with the newly-weds, including MasterChef co-host and Gregg's best man John Torode and his girlfriend, actress Lisa Faulkner.
Masterchef: The Professionals' judge Monica Galetti was also in attendance, along with around 40 close family and friends. According to the Sunday Mirror, the ceremony was an intimate affair, with up to 120 people joining for the evening reception later that day.
Anne-Marie and Gregg met in 2013 on Twitter when Anne-Marie messaged the chef seeking cooking advice, asking if rhubarb went with duck, and the pair have been inseparable ever since.
Speaking about the moment he saw Anne-Marie's picture after she tweeted him, Gregg said: 'I looked at her picture and thought, "Oh wow!" so I started flirting and sent her my number.
'At first she couldn't tell if it was me or a lookalike. But she soon realised once we got to a restaurant and people started saying, "Hello, Gregg".'
Gregg, who has two children with his second wife Denise - Tom, 22, and Libby, 19 - popped the question after the couple's two-year anniversary in December 2014. The pair were originally set to marry in April, but were forced to postpone due to work commitments and instead moved the date to August.
In an interview with the Mirror earlier this year, Gregg addressed the 21-year age gap between him and his now-wife: 'I have been uncomfortable with it, yeah. It depends on where I am with her.
'Out in a nice restaurant it's fine because you get lots of older blokes with young women there, but the other day we were in Bluewater Shopping Centre in Kent and she wanted to hold my hand and I was very self-conscious about that. I felt as if everyone was looking at me.'
Congratulations to the happy couple!