Serene Highness
The reigning Prince of Monaco, Albert II, is addressed as "His Serene Highness". His wife, children and younger sister, Princess Stéphanie, are also referred to as "Serene Highness". His elder sister, Princess Caroline, was also styled "Her Serene Highness" prior to her 1999 marriage, but is styled "Royal Highness" since then, even during the period when she was officially "The Hereditary Princess of Monaco" as heiress presumptive to the throne. In French, both male and female versions are "Son Altesse Sérénissime" ("S.A.S."), which translates, literally, as "His/Her "Most" Serene Highness".