The 42-year-old and Formula 1 boss Christian, 40, posted the ad in The Times.
BRITNEY SPEARS SHARES ADORBALE FIRST SELFIE WITH NEW BOYFRIEND
It read: "Mr C.E.J. Horner OBE and Miss G.E. Halliwell.
"The engagement is announced between Christian, the son of Mr and Mrs G.M. Horner and Geraldine, daughter of the late Mr L.F. Halliwell and Mrs A. Parkinson."
Geri and Christian went public with their relationship in March this year, but they have been friends since 2009.
JENNIFER ANISTON AND JUSTIN THEROUX HAVE 'SET THEIR WEDDING DATE'
Former Spice Girl Geri has seven-year-old daughter Bluebell from her relationship with Sacha Gervasi.
Christian has one-year-old daughter Olivia from a previous relationship.
Geri's former partners include Chris Evans, Russell Brand and Duncan James.
It seems that old fashioned newspaper announcements are becoming a bit of a trend.
Last week actor Benedict Cumberbatch and theatre director Sophie Hunter announced their engagement via The Times.
Congratulations to Geri and Christian!