Slartibartfast was a magrathean biped living on the planet Magrathea. During the planet's societal height, he constructed the coastlines of continents on planets manufactured by Magrathea; in particular, he specialised in fjords. He won an award for his work on Norway.

Slartibartfast encountered Arthur Dent when he (along with Zaphod Beeblebrox, Ford Prefect, Trillian and Marvin) traveled to Magrathea. He showed Dent his newly-redesigned Africa, with plenty of fjords because they give a "baroque" feel to a continent. Slartibartfast shared the historical records with Arthur of the story of Deep Thought and the Answer to the Ultimate Question.

Slartibartfast also later assisted Arthur and Ford, through the use of his starship Bistromath, in combatting the menace of the Krikkiteers