Geri Halliwell – who recently married Christian Horner – posted a snap from the group's early days, writing: "HAPPY BIRTHDAY @officialmelb Wishing you love health happiness success. Xx [sic]"
Baby Spice aka Emma Bunton tweeted a touching selfie with her friend, adding: "Happy birthday @officialmelb the big 40. Love you so much. Xx [sic]"
Victoria Beckham finished off the birthday tributes. Posh Spice shared a photo of her and Scary on stage and gushed: "Happy birthday Melanie. X I love u x Victoria x [sic]"
Sporty Spice Melanie C decided not to join in with the nostalgic posts but, as she's busy being a judge on Asia's Got Talent right now, we'll let her off.
Mel B was obviously feeling the birthday love as she posted a selfie with the caption: "You guys are the best."
At the beginning of the month Mel C, Emma and Geri joined Victoria in Marrakech to celebrate husband David's 40th birthday.
And two weeks ago Emma was present to see Geri become Mrs Horner as she married Formula 1 boss Christian in a romantic ceremony in Woburn.
Can we just have an actual reunion now, please?