The Monaco palace said he would marry Colombian heiress Tatiana Santo Domingo on August 31, but gave no details on the wedding. The couple have been engaged for a year and she gave birth to a son in March.
The 29-year-old Casiraghi is the nephew of Monaco's ruling sovereign, Prince Albert II, who himself ended decades of bachelorhood in 2011 when he wed South African former Olympic swimmer Charlene Wittstock.