The 32-year-old musical artist, whose real name is Claire Boucher, and her SpaceX and Tesla mastermind boyfriend welcomed their first child together on Monday, Musk tweeted.
Musk, 48, shared a photo of himself holding the newborn in the hospital early Tuesday morning. He first broke the news on Twitter Monday, when a user asked him for updates on the baby.
"A few hours away!" Musk wrote. About four hours later, he added, "Mom & baby all good."
And later, in response to another Twitter question, he replied simply, "Boy." USA TODAY has reached out to a representative for Grimes for more information.
This is Grimes' first child. Musk has five sons – a set of twins and a set of triplets – from his previous marriage.
Grimes first sparked pregnancy rumors on Instagram in January by posting a nude photo of herself with a fetus Photoshopped over her visible baby bump.
She didn't caption the picture, leaving fans to speculate whether the photo was a pregnancy announcement or just the latest example of her artistic expression.
Boy or a girl elon? 🍼👶— Pranay Pathole (@PPathole) May 5, 2020
In February, Grimes confirmed on Instagram she was 25 weeks pregnant and struggling to "cope with working and having a baby."
"This whole thing has been a bit of an ordeal," Grimes captioned a selfie in the post. "Had some complications early on, a decent second trimester but starting to hurt everywhere at 25 wksz. What were yalls experience w this stuff like?"
The Canadian singer said she didn't fully "understand what I was getting into" or the physical toll pregnancy takes on your body
"I feel like I was woefully ill prepared cuz I dunno if pregnancy is as visible or discussed as it should be," Grimes wrote. "It’s been good too, but it makes working a lot harder. Good at writing and having lots of wild ideas tho, but anything physical is hard. Im also way more emo and less capable of bravery in the face of haters online and stuff haha."
Grimes talks 'profound' decision to have baby with Elon Musk: 'I have sacrificed my power'
In her Rolling Stone profile published in March, Grimes opened up about the "tragedy" that comes with carrying a child, "even though it's this great thing."
"For a girl, it’s sacrificing your body and your freedom," Grimes said. "It’s a pretty crazy sacrifice and only half of the population has to do it."