Kate Middleton, Prince William Welcome Baby Boy: Stars React on Twitter

Joan Rivers; Jack Osbourne; Cheryl Cole
See what stars like Joan Rivers, Jack Osbourne and Cheryl Cole are saying on Twitter about the arrival of Kate Middleton and Prince William's baby boy on July 22 Daniel Zuchnik/Getty Images; John Sciulli/WireImage; Mike Marsland/WireImage

It's official: Duchess of Cambridge Kate Middleton and Prince William have welcomed a baby boy on Monday, July 22. "Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 4:24 p.m. The baby weighs 8 lbs 6 oz," the Palace confirmed in a statement on Twitter. "The Duke of Cambridge was present for the birth. The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry & families have been told and are delighted. Her Royal Highness and her child are both doing well and will remain in hospital overnight."

Following the announcement, stars have taken to Twitter to congratulate the couple and welcome His Royal Highness. See what they're tweeting below:

First Lady Michelle Obama: "Congratulations to The Duke and Duchess of Cambridge on the birth of their son! Being a parent is the best job of all."

Joan Rivers: "Congratulations to Kate & William on the birth of their baby boy! So relieved that his name won't include the words Ivy or Apple."

Melissa Gilbert: "Welcome royal baby boy!!!"

Louise Roe: "Congrats to William and Kate on the birth of their baby BOY! #RoyalBaby"

Ramona Singer: "A Prince! How exciting! #RoyalBaby #itsaboy"

Tiffany Thornton: "King is born! Loving this royal baby excitement. congrats to Will and Kate"

Cheryl Cole: "Congratulations to William and Kate!! So happy they have a healthy baby and everyone is good. Can't wait to see him now #Royalbaby"

Jack Osbourne: "EPIC!!!! a new prince was born. its like real life Game of Thrones #royalbaby"

Josh Groban: "I know it's a boy, I'm watching it on the dang web cam. It's gurgling."

Chrissy Teigen: "BABY BOY good thing I didn't tweet my prediction of ginger girl."

Melissa Joan Hart: "Congratulations to the royal family on the new little Prince! Welcome to the world little man! #royalbaby" 

Lisa Rinna: "It's a BOY! #royalbaby I had a feeling it was a boy! Yay! Congrats Will and kate!"

Sign up now for the Us Weekly newsletter to get breaking celebrity news, hot pics and more delivered straight to your inbox!

Want stories like these delivered straight to your phone? Download the Us Weekly iPhone app now!