"I'm very proud to say our son has arrived yesterday at 7pm," she wrote. "2 weeks late and a big one 9lbs 10 and he's perfect!"
The new arrival is the couple's first child together. They have yet to reveal what they have named their bundle of joy, or give fans a glimpse of him in a photo.
Chris and sports journalist Charlotte first met in 2012 when she interviewed him at a golf competition. The couple got engaged in August 2013 and were due to marry this year, but have decided to postpone their nuptials until 2015.
Charlotte, a former competitor on the diving reality show Splash!, announced that they were expecting a baby in June, revealing she was already four months pregnant.
Charlotte has been sharing photos of her growing baby bump on Twitter
"Thanks for all the congratulations!" she wrote on Twitter. "We are very pleased and excited to be expecting a baby this year!!"
While this is Charlotte's first child, Chris is already a father to four children from his first marriage with ex-wife Belinda. They split in 2011 after 19 years together.
Earlier this year Charlotte revealed that she gets on well with Chris' children, and was keen to have her own.
"It's all geared towards having babies," she said of the couple's future. "We both want them and want to be nearer to mum and dad so they can help. Luckily Chris wants more, we're both excited."