Arthur is a thirty-year-old, dark-haired Englishman who lives a quiet and unremarkable life until his home is slated for demolition to make way for a bypass. Driven by nostalgia and a desire for normalcy, he finds himself thrust into a confusing galactic journey entirely against his will. He struggles to process the loss of his home planet while dealing with bizarre alien companions.

Ford poses as an out-of-work actor but is actually an alien researcher from the vicinity of Betelgeuse. He has been stranded on Earth for fifteen years working on an update for the electronic book The Hitchhiker's Guide to the Galaxy. He masks his extraterrestrial nature with eccentric behavior, maintaining a calm demeanor and ensuring he always has his bath towel.

Zaphod is the newly elected President of the Imperial Galactic Government, a position he treats entirely as a public relations stunt. He possesses two heads and three arms, cultivating a larger-than-life outlaw persona to draw attention away from actual political power. He relies on bravado and charm to survive the chaos he actively creates.

Jeltz is a bureaucratic captain in the Galactic Civil Service who commands the Vogon demolition fleet. Like all Vogons, he is highly unevolved, thoroughly unpleasant, and violently opposed to hitchhikers secretly boarding his vessel.

Trillian is a highly intelligent astrophysicist and mathematician from Earth who leaves the planet with Zaphod to avoid the drudgery of unemployment. While Zaphod acts impulsively, she provides a calm and perceptive counterweight to his exaggerated antics. She brings two white mice with her as companions on her journey.

Marvin is a robot manufactured by the Sirius Cybernetics Corporation with a Genuine People Personality that makes him chronically depressed and pessimistic. He expresses constant contempt for humanoids and resents performing even the simplest tasks around the ship.

Prosser is an emissary from the local council charged with clearing the way for a new bypass. He is an unremarkable bureaucrat who despises confrontation and wishes someone else would handle the angry homeowner blocking his bulldozers.

Slartibartfast is an elderly Magrathean designer who specializes in creating planetary coastlines. He is an eccentric but gentle man who recently awakened from centuries of hypersleep to resume his planetary construction duties.

Deep Thought is a massive, city-sized supercomputer designed by a species of hyper-intelligent beings. Built explicitly to calculate the ultimate answer to life, the universe, and everything, it speaks with infinite majesty and calm.

Majikthise is a philosopher who fears that a supercomputer solving the mysteries of the universe will put academics out of a job. He is primarily concerned with protecting his lucrative media market and speaking fees.

Vroomfondel is a loud and demanding philosopher who insists on rigid boundaries for academic inquiry. He threatens labor action to prevent machines from answering metaphysical questions.

Phouchg is a philosopher who assesses the great computer's output. Like his peers, he displays a shallow intellectual focus, complaining about the dull name given to a majestic new creation rather than appreciating its significance.

Benjy is one of Trillian's pet white mice who travels with her aboard the Heart of Gold. He represents a quiet, seemingly harmless presence on the ship.

Frankie is the second of Trillian's white mice brought aboard the spaceship. He observes the humans carefully from his enclosure.