Dogmatix is a fictional character, a dog who belongs to Obelix in the Asterix comics.

His role is minor in most of the stories, significant mainly as a 'bone' of contention between Asterix and Obelix as to whether he should be allowed to accompany them on their adventures. However, occasionally he has fulfilled an important part of the plot development. Dogmatix is the only main character which is an animal.

In Asterix and Cleopatra he follows the Gauls into a pyramid in which they are lost and guides them safely out (with the promise of lots of bones).

His friendship with Pepé in Asterix in Spain causes Obelix to become very jealous.

The name Dogmatix, a pun on the word dogmatic, is the English-language adaptation of the French original Idéfix, itself a pun on the French expression idée fixe (fixed idea), a term used to describe a dominant theme in music, literature or philosophy, associated with the 19th century French composer Hector Berlioz (and therefore instantly recognizable to a reader of the French original comic).