She joins from Sony Europe, where she has been director of corporate comms for the past two years.
Osman will take up the role in June, replacing Harverson, who is leaving to set up an agency with DJ Collins, Google's VP public policy and comms EMEA.
Osman previously worked as director of comms at the BBC for eight years and held senior comms positions at other media organisations including BSkyB. She was also a consultant for the China Media Centre at the University of Westminster and for the brand agency Make Believe.
The Prince of Wales' principal private secretary William Nye commented: ‘Sally is a very accomplished communications professional who will serve The Prince of Wales and The Duchess of Cornwall very well.
'She has a formidable record of achievement in the public and private sector, and an enviable reputation for straightforwardness and integrity.’
Osman added: ‘It is a great honour to be appointed to this role and a big responsibility. I hope my communications experience can help support Their Royal Highnesses in the extensive work they do and commitment they give to so many important issues, organisations and individuals.’