The Book of Thomas the Contender, also known more simply as the Book of Thomas (not to be confused with the Gospel of Thomas), is one of the books of the New Testament apocrypha represented in the Nag Hammadi library, a cache of Gnostic gospels secreted in the Egyptian desert. The title derives from the first line of text.

"The secret words that the savior spoke to Judas Thomas which I, even I, Mathaias, wrote down, while I was walking, listening to them speak with one another."
The colophon appended to the text gives the title The Contender writing to the Perfect.

There are two competing theories as to the composition of the text
Firstly, since it is only the initial 3/5 which constitute dialogue, with the remainder being a monologue, it may have originally been two works, one of dialogue, one of monologue.

Alternately, and not in the least because of the two titles, the work is thought to have originated as a letter, with a name of the form Epistle of the Contender, written by a Jew who upheld Hellenic philosophy. The text is thought to have later been given a christian setting and converted into a dialogue, in a similar manner to other works.

An additional consideration is that, since the scribe writing the text is named as Matthias, this work may actually be the lost Gospel of Matthias. The dialogue can also be read as an internal conversation between Jesus and his lower self, Judas Thomas, the twin (contender for supremacy of the soul). The New Testament's "doubting" Thomas and Judas "the betrayer" could also be symbolic and descriptive of this internal battle between the Christ Self and ego identity.
The content of this work is quite hyperbolic and gnostic in style, in the sense of imparting a private, arcane knowledge related to good versus evil, and while it lacks references to the elaborate gnostic cosmology, its gnostic allusions to the pleroma and light versus fire clearly point to its origins. q

Then the savior continued and said, "O unsearchable love of the light! O bitterness of the fire that blazes in the bodies of men and in their marrow, kindling in them night and day, and burning the limbs of men and making their minds become drunk and their souls become deranged... Woe to you, captives, for you are bound in caverns! You laugh! In mad laughter you rejoice! You neither realize your perdition, nor do you reflect on your circumstances, nor have you understood that you dwell in darkness and death! On the contrary, you are drunk with the fire and full of bitterness. Your mind is deranged on account of the burning that is in you, and sweet to you are the poison and the blows of your enemies! And the darkness rose for you like the light, for you surrendered your freedom for servitude! You darkened your hearts and surrendered your thoughts to folly, and you filled your thoughts with the smoke of the fire that is in you! (Book of Thomas the Contender)

The gnostic content in the texts of the Nag Hammadi trove can be argued to be often identical to Jesus' conceptual content, but the metaphorical language and symbolism are strikingly different. "The Book of Thomas the Contender," and it's guidance in overcoming ego "lusts/attachments" differs markedly with Jesus' gentler, more practical psychological approach in the Four Canonical Gospels and The Gospel of Thomas.

"The Book of Thomas the Contender" may be a gnostic text imbued with Judeo-Hellenic philosophy, having been adjusted for a Christian audience.