The Restaurant at the End of the Universe (1980, ISBN 0345391810) is the second book in the Hitchhiker's Guide to the Galaxy comedy science fiction series by Douglas Adams. It was originally published by Pan Books as a paperback.

It takes its name from Milliways, the Restaurant at the End of the Universe, one of the settings of the book.

The Restaurant at the End of the Universe continues the story from where The Hitchhiker's Guide to the Galaxy ended. Arthur Dent, Ford Prefect, Trillian, and Zaphod Beeblebrox have just left Magrathea when they are attacked by a Vogon ship. They are rescued by Zaphod's ancestor Zaphod Beeblebrox the Fourth, but Zaphod and Marvin unaccountably vanish, to turn up at the offices of the Guide. They are looking for Zarniwoop, who has gone on an intergalactic cruise in his office.

When they meet Zarniwoop, Zaphod turns out to have a model of the Heart of Gold in his jacket pocket. This grows back to full size, and the heroes are at last on their way to the Restaurant at the End of the Universe (where Zaphod had promised to take them at the end of the previous book). When leaving the restaurant, to avoid Zarniwoop Zaphod steals a spaceship, which turns out to be a stuntship belonging to Disaster Area, programmed to dive into a star to provide backing effects for a rock concert.

The only teleport on the ship has no guidance system, so they have to go wherever it takes them. Arthur and Ford end up in the Golgafrinchan Ark Fleet Ship B, which crash-lands on prehistoric Earth. Zaphod and Trillian return to the Heart of Gold, which is commandeered by Zarniwoop to complete his mission: to discover who really rules the Universe. (Marvin had to stay on the stuntship to operate the teleport: how he got from there to Squornshellous Zeta, where he reappears in Life, the Universe, and Everything is not known.)

The plot is based on the last eight Fits of the original radio series (The Hitchhiker's Guide to the Galaxy was based on the first four). The fragments of the plot are rearranged, and some do not appear at all. For example, Arthur and Ford were stranded on prehistoric Earth at the end of Fit the Sixth and later rescued; they are now stranded at the end of the book, and the episode of their rescue is deleted. The episodes taking place on the planet Brontitall are transferred to the Frogstar and hugely compressed, omitting several characters who do not appear elsewhere. Most significantly, in the radio series the ship stolen from the Restaurant at the End of the Universe belonged not to Disaster Area, but to the Admiral of the Fleet of a warlike "super-evolutionary" race, who could evolve into any shape in a matter of seconds. Zaphod and Marvin both escaped when a member of this race fortuitously evolved into an escape capsule, and turned up at the Hitchhiker's Guide offices on Ursa Minor Beta, which came after the Restaurant episodes in the radio series. The fact that Marvin also escaped is one loose end that the new radio series fails to tie up adequately, or indeed at all.