A "Conceptual Character" or "Conceptual Personae" is a notion developed by Gilles Deleuze and Félix Guattari in their co-authored book 'What is Philosophy?". It serves to designate fictitious or semi-fictional characters, created by one or more authors in order to convey one or more ideas. What makes a personae or character "conceptual" is simply their bearing some concept represented of convyed by them. Even if originally a historical individual may have existed, he was subsequently used by authors who took it up as their own.
According to Deleuze and Guattari:
The conceptual persona is not the philosopher's representative but, rather, the reverse: the philosopher is only the envelope of his principal conceptual persona and of all the other personae who are the intercessors [ intercesseurs], the real subjects of his philosophy. Conceptual personae are the philosopher's "heteronyms," and the philosopher's name is the simple pseudonym of his personae. I am no longer myself but thought's aptitude for finding itself and spreading across a plane that passes through me at several places. The philosopher is the idiosyncrasy of his conceptual personae. The destiny of the philosopher is to become his conceptual persona or personae, at the same time that these personae themselves become something other than what they are historically, mythologically, or commonly (the Socrates of Plato, the Dionysus of Nietzsche, the Idiot of Nicholas of Cusa). The conceptual persona is the becoming or the subject of a philosophy, on a par with the philosopher, so that Nicholas of Cusa, or even Descartes, should have signed themselves "the Idiot," just as Nietzsche signed himself ''the Antichrist" or "Dionysus crucified." In everyday life speech-acts refer back to psychosocial types who actually attest to a subjacent third person: "I decree mobilization as President of the Republic," "I speak to you as father," and so on. (What is Philosohy, 64).