Thierry Meyssan (French: [tj??i m?s?~]) is a French journalist, conspiracy theorist and political activist.
He is the author of investigations into the extreme right-wing (particularly about the National Front militias, which are the object of a parliamentary investigation and caused a separation of the extreme right-wing party), as well as into the Catholic church (Opus Dei, for example).
Meyssan's book 9/11: The Big Lie (L'Effroyable imposture) challenges the official account of events of the September 11 terrorist attacks.