The 36-year-old TV and radio presenter, who counts model Erin O'Connor and Nip/Tuck star Joely Richardson among his exes, proposed while they were on holiday in Paris.
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Jamie Theakston and fiancee Sophie Siegle: The radio and TV presenter proposed to Sophie in Paris
Jamie with old flames model Erin O' Connor and Nip/Tuck actress Joely Richardson
The couple have been together since they met at the Oscars two years ago.
Siegle works at private members club Soho House.
Theakston said: "We are both delighted and although a date has not been set we are hoping to get married before the end of the year."
The Heart 106.2 DJ recently said: "My mum started nagging me when I was 19, saying, 'Why aren't you married yet?'
"She wants to be a grandmother and I hope she doesn't have to wait too long.
"I wouldn't be surprised at all if I was married in two years' time."
Theakston, who was photographed in a Mayfair brothel in 2002, has also been linked in the past to Amanda Holden and Natalie Appleton.
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