Who is C. Auguste Dupin and of what is he considered by many to be the first?

C. Auguste Dupin was a fictional detective from the works of American author Edgar Allan Poe (1809-1849). Many consider him to be the first literary detective and Poe's works the first detective fiction.

Dupin first appeared in Poe's short story "The Murders in the Rue Morgue" (1841). He subsequently figures again in "The Mystery of Marie Rogêt" (1842) and finally in 1844's "The Purloined Letter".

Dupin predates the word "detective", while Poe's work laid the groundwork for many subsequent elements of the detective fiction genre.

https://en.wikipedia.org/wiki/C._Auguste_Dupin