Professor Cuthbert Calculus (French: Professeur Tryphon Tournesol [pʁɔ.fɛ.sœʁ tʁi.fɔ̃ tuʁ.nə.sɔl], meaning "Professor Tryphon Sunflower") is a fictional character in The Adventures of Tintin, the comics series by Belgian cartoonist Hergé. He is Tintin's friend, an absent-minded professor and half-deaf physicist, who invents many sophisticated devices used in the series, such as a one-person shark-shaped submarine, the Moon rocket, and an ultrasound weapon. Calculus's deafness is a frequent source of humour, as he repeats back what he thinks he has heard, usually in the most unlikely words possible. He does not admit to being near-deaf and insists he is only a little hard of hearing in one ear.

Calculus first appeared in Red Rackham's Treasure (more specifically in the newspaper prepublication of 4–5 March 1943), and was the result of Hergé's long quest to find the archetypal mad scientist or absent-minded professor. Although Hergé had included characters with similar traits in earlier stories, Calculus developed into a much more complex figure as the series progressed.