Charles-Albert-Marie Costa, Marquis de Beauregard (24 May 1835 – 15 February 1909) was a French historian and politician.

[5] After being educated in Belgium,[4] Beauregard was general counsel of Savoie from the time of the annexation of the Duchy of Savoy to France on 14 June 1860, following the signature of the Treaty of Turin on 24 March 1860, after which he lived in Paris.

After the war, he retired from politics to devote himself to his writing on the subject of his family history, Savoy and the monarchy.

Beauregard's most important works are a trilogy on King Charles Albert of Savoy, and Historical Memoirs of the Royal House of Savoy, based on documents held in his family archive and which was a completion of the work begun by his grandfather in 1816.

[4] He was a member of the Académie des sciences, belles-lettres et arts de Savoie, and its president from 1887 to 1889.