Titus Cornelius Celsus, Roman usurper under Gallienus, one of the Thirty Ty­rants enumerated by Trebellius Pollio.

Celsus (Greek: ) was a 2nd century Greek philosopher and opponent of Christianity. He is known to us mainly through the reputation of his literary work, The True Word (Account, Doctrine or Discourse), almost entirely reproduced in excerpts by Origen in his counter-polemic Contra Celsum of 248, 70 or 80 years after Celsus wrote.