Porthos is a fictional dog in the Star Trek: Enterprise universe. He is the pet of Captain Jonathan Archer, and an English Beagle. He is named after the fictional character Porthos, one of The Three Musketeers.

He is also a connoisseur of fine cheeses; Cheddar cheese, Monterrey Jack and Gruyere being his favourites.

T'pol is sensitive to the smell of Porthos, since Vulcanss have enhanced sensory abilities.

Porthos was nearly killed when he contracted a deadly pathogen on the Kreetassan homeworld.