Sienna Miller has revealed she has become a mother for the third time.
The 44-year-old actress shared the happy news whilst doing press for her latest project, Jack Ryan: Ghost War, though she kept specific details about the newborn private.
Speaking to E! News, Ms Miller said: "It's happened. I have a tiny baby next door."
The star admitted the early days of parenthood were taking their toll on her sleep schedule.
Sienna Miller has given birth to her third child
|GETTY
"It feels like stringing sentences together is a bit challenging," she explained. "I'm on very little sleep but I'm madly in love with my baby."
Ms Miller had confirmed her pregnancy towards the end of last year, and this latest arrival marks her second child with partner Oli Green.
The new baby joins Ms Miller's growing family, which includes her eldest daughter Marlowe, now 13, from her previous relationship with actor Tom Sturridge.
Ms Miller also has a two-year-old daughter with Mr Green, whose name the couple have chosen to keep out of the public eye.
Sienna Miller has welcomed the newborn with partner Oli Green
|GETTY
Mr Green, who is 29, has been in a relationship with Ms Miller for several years.
The actress has previously spoken about how she initially found their 14-year age gap somewhat inconvenient when they first met.
"I wasn't like, 'I'm gonna get a younger boyfriend,'" she told British Vogue. "It was more, 'F***! Why are you young? That's so annoying.'"
Ms Miller has spoken candidly about how motherhood feels markedly different at this stage of her life compared to when she first became a parent.
LATEST DEVELOPMENTS
Sienna Miller has two other children
|GETTY
"Having had a baby at 29, and then having a baby at 42, and now 44, it's so much easier when you don't have the conflict of feeling scattered and like you want to be doing X, Y, Z," she told Glamour magazine.
The actress described her thirties as a period of "chaos" but said reaching her forties brought a sense of self-assurance.
"By the time you hit 40, you're like, 'I kind of know who I am. I don't really give a s*** about what anyone else thinks.
"We don't judge men who are having kids in their 80s. Why on earth is there any sort of narrative?"
In Jack Ryan: Ghost War, Miller takes on the role of MI6 officer Emma Marlowe, a character she described as a departure from her previous work.
"I loved it. I haven't done anything really like this before and to play someone who is incredibly unapologetic, incredibly tough and bold and brave and pretty funny and dry and very cool -- it was thrilling," she said.
The actress is hopeful the action role might finally capture her teenage daughter's attention, noting that Marlowe "couldn't be less interested in my career if I tried."
Ms Miller suggested the character's name might prove a useful hook.
"I thought people calling me 'Agent Marlowe' would hook her. So maybe she'll finally watch a film of mine," she said.