Auguste was the illegitimate son of Michel-Louis-Étienne, Count Regnaud de Saint-Jean d'Angély,[1] and of his mistress Marie-Louise Chenié, who died shortly after his birth, he was recognised by his father some months later and adopted by the latter's wife in 1795.

[citation needed] Under the Second Empire, he went through the Crimean and Italian campaigns, and ultimately was created Marshal of France in 1859 for bravery at the Battle of Magenta.

[citation needed] Since his father never married his mother (who died some months after the redaction of a marriage contract), Regnaud de Saint-Jean d'Angély had not been able to succeed to his title of count.

Notwithstanding, Napoléon III granted him the title again in November 1864, with the special permission to pass it at his death to the husband of his adoptive daughter, Edmond Davillier.

[citation needed] Marshal Regnaud de Saint-Jean d'Angély died in Cannes in 1870 and was buried in the Hôtel des Invalides in Paris.