
Celsus ya da Kelsos (Eski Yunanca: Κέλσος Kélsos, Latince: Celsus), milattan sonra 2. yüzyılın ikinci yarısında yaşamış Platon geleneğine bağlı bir filozoftur. Hristiyanlığa karşı yazdığı eleştirel metin ile tanınmaktadır. Ayrıca Celsus, "İsa'nın mucizelerini sihirle gerçekleştirdiğini" savunarak İsa'nın mucizelerine ve İsa'nın kendisine değindi. Bu metin günümüze bütünüyle ulaşmasa da, kilise babası Origenes'in Celsus'a yönelik yazdığı reddiye Contra Celsum sayesinde rekonstre edilebilmektedir.
According to Celsus Jesus performed His miracles by sorcery (γοητεία); ditto in II, 14; II, 16; II, 44; II, 48; II, 49 (Celsus puts Jesus' miraculous signs on a par with those among men).
Celsus calls Jesus a sorcerer. He argues that the miracles of Jesus are on the same level as: 'the works of sorcerers who profess to do wonderful miracles, and the accomplishments of those who are taught by the Egyptians, who for a few obols make known their sacred lore in the middle of the market-place and drive daemons out of men and blow away diseases and invoke the souls of heroes, displaying expensive banquets and dining tables and cakes and dishes which are non-existent, and who make things move as though they were alive although they are not really so, but only appear as such in the imagination.'
To disprove the deity of Christ required an explanation of his miracles which were recorded in scripture. Celsus does not deny the fact of Jesus' miracles, but rather concentrates on the means by which they were performed. Perhaps influenced by rabbinical sources, Celsus attributes Jesus' miracles to his great skills as a magician.