What nationality is the fictional detective Hercule Poirot?

Hercule Poirot (pronounced in English ɛʀkyl pwaʀo) is a fictional Belgian detective created by Agatha Christie. Along with Miss Marple, Poirot is one of Christie's most famous and long-lived characters: he appeared in 33 novels and 54 short stories. Poirot has been portrayed on screen, for films and TV, by various actors including Albert Finney, Peter Ustinov, Ian Holm, Tony Randall, Alfred Molina, David Suchet, Kenneth Branagh, and John Malkovich.

Source: Agatha Christie Wiki