Andrew Mountbatten-Windsor has been arrested in England.
Thames Valley Police didn't name the former prince, but say a man in his 60s is in custody, on suspicion of misconduct in public office.
Cars, reportedly unmarked police vehicles, were seen arriving at Sandringham this morning.
Today is his 66th birthday.
His brother, Britain's King Charles, stripped him of his titles last year, as well as his home, following allegations surrounding his links to the late paedophile Jeffrey Epstein.
Documents claim he shared sensitive information with the convicted sex offender, while working as a trade envoy for Britain.
Andrew has consistently denied any wrongdoing.