Tom Daley and husband Dustin Lance Black announced the birth of their in a brief announcement printed in the Times newspaper on Saturday.
The baby has been named Robert Ray, it was announced.
The Times announcement read: "BLACK-DALEY: On 27th June 2018 to Thomas Robert Daley and Dustin Lance Black, a son, Robert Ray.”
The couple revealed they were expecting a child through a surrogate in February, and the three-time World Champion diver has also said he wants to be as good a dad as his father, who was also called Robert and died in 2011.
Daley spoke of how the impending fatherhood changed his perspective as he competed at the Commonwealth Games on the Gold Coast in April.
He said: "It’s been such a crazy experience. It changes your outlook on life.
"Even on a plane. I’m never scared of flying – and as soon as there was any turbulence I was like 'oh my God', because there’s more than my life I have to care about now.
"It made me feel a bit more nervous. It changes your perspective on absolutely everything."
“It’s all filled with excitement, getting everything ready, feeling like you don’t really know what’s going to happen.
“The fear of what might happen and the excitement. There’s so many emotions that come with being an expectant father.”
Daley and Black also announced their engagement in a similarly understated way in 2015, with an announcement reading: “The engagement is announced between Tom, the son of Robert and Debra Daley of Plymouth, and Lance, son of Jeff Bisch of Philadelphia and Anne Bisch of Lake Providence.”
Black, 44, is an American film director and producer. He won an Oscar for best original screenplay for Milk, a film based on the life of gay rights activist and politician Harvey Milk.