His/Her Ducal Serene Highness ( abbreviation: HDSH) was a style used by members of certain

ducal Duke is a male title either of a monarch ruling over a duchy, or of a member of royalty, or nobility. As rulers, dukes are ranked below emperors, kings, grand princes, grand dukes, and sovereign princes. As royalty or nobility, they are ran ...

families, such as those of Nassau, Braganza, and the

Ernestine duchies The Ernestine duchies (), also known as the Saxon duchies (, although the Albertine appanage duchies of Weissenfels, Merseburg and Zeitz were also "Saxon duchies" and adjacent to several Ernestine ones), were a group of small states whose num ...

(until 1844). This treatment is superior to

Serene Highness His/Her Serene Highness (abbreviation: HSH, second person address: Your Serene Highness) is a style used today by the reigning families of Liechtenstein, Monaco and Thailand. Over the past 400 years, it has also used as a style for senior members ...

because it takes the adjective ducal (relative at duke). The

Saxon duchies The Ernestine duchies (), also known as the Saxon duchies (, although the Albertine appanage duchies of Weissenfels, Merseburg and Zeitz were also "Saxon duchies" and adjacent to several Ernestine ones), were a group of small states whose numb ...

of Meiningen, Gotha and Altenburg dropped the style in favor of ''Highness'' in 1844.Memoirs of Ernest II
(1888), p.137

References

Styles (forms of address) Royal styles {{Royal-stub