The Prime Minister and his partner Carrie Symonds have announced the birth of a baby boy.
A spokesman for the couple said: "The Prime Minister and Ms Symonds are thrilled to announce the birth of a healthy baby boy at a London hospital earlier this morning. Both mother and baby are doing very well.
"The PM and Ms Symonds would like to thank the fantastic NHS maternity team."
The birth comes just weeks after Mr Johnson was admitted to an intensive care unit with coronavirus. Ms Symonds also had symptoms of the virus.
Not known if PM will take paternity leave
In March Mr Johnson, 55, and Ms Symonds, 32, announced that hey were expecting a baby in "early summer".
Mr Johnson has previously hinted that he intends to take paternity leave, although it is not known if this remains the case after his recent time off.
He will not appear at Prime Minister's Questions in the Commons on Wednesday afternoon.
The baby is Ms Symonds' first child, while Mr Johnson is known to have fathered five.
The new arrival is the third baby born to a serving prime minister in recent history.
Tony Blair's wife Cherie gave birth to son Leo in May 2000, three years after her husband's first election victory, and David Cameron and wife Samantha welcomed daughter Florence in 2010.
The pair and their newborn have been inundated with positive messages from politicians from across the political spectrum.
Health Secretary Matt Hancock tweeted his congratulations saying: "So thrilled for Boris and Carrie. Wonderful to have a moment of unalloyed joy!"
Leader of the opposition Sir Keir Starmer also congratulated the PM and his partner, tweeting: "Wonderful news. Many congratulations to Boris Johnson and Carrie Symonds."
First Minister Nicola Sturgeon tweeted: "Some good news - sending congratulations to Carrie and the PM. And wishing health and happiness to the wee one."
Labour MP Jess Phillips tweeted: "Congratulations to the Prime Minister and @carriesymonds. It gets better after the first 8 weeks, or your standards drop so dramatically in that time that you think it's got easier. I wish them all well."