The baby girl, who weighed in at 7lbs 10oz, was born on Sunday at Cedars Sinai Medical Center in Los Angeles.
Fellow Spice Girl Emma Bunton: "Big kiss to Victoria Beckham can't wait to meet your gorgeous little girl! (sic)."
Mel B, currently also pregnant: "Congrats!!! Yipeee another spice baby is born, damn i wish it was me this AM cos I feel like I'm about to Pop!"
Apprentice host Lord Alan Sugar: "Congrats to Beckhams on the birth of their new baby girl."
David Beckham's sister Joanne Beckham: "Big congrats to my sister in law @victoriabeckham and my big bro on the birth of my beautiful niece :) can't wait 2 see u all xx"
Boy George: "Ah, little girl for the Beckhams, congratulations!"
Chatshow host Ellen DeGeneres: "Congratulations to David and @VictoriaBeckham and their new baby girl! I can't wait to meet her."
Reality TV star Louis Spence: "@victoriabeckham congrats to you both, what a lucky girl, what a vintage wardrobe she's gonna have.xx"
Singer Beverley Knight: "So chuffed for David and Victoria Beckham! Their lovely baby girl entered the world today!"
Manchester United striker Michael Owen: "I hear Victoria Beckham has just given birth to a baby girl. Great news."
Model Danielle Lloyd: "This time last year I'd just giving birth 2 my beautiful baby Archie Luv him so much Congratulations 2 @victoriabeckham on birth of Harper X"
The Thick of It star Chris Addison: "Other names considered by the Beckhams: Groucher Six, Chicer Five, Zepper Nine and Gummer Twelve."
Rufus Hound: "Harper Seven was also the name of Bobby Ball's Netball Team. They made the semi's after Blakes Seven didn't show up in the quarter-final."
Comedian Robin Ince: "The Beckhams have merely given their new child this name out of kindness to all comedians having trouble writing their Edinburgh shows."