Ultima III: Exodus, the third in the Ultima series, is considered one of the most influential computer role-playing games in history. Released in 1983, it was the first Ultima game published by Origin Systems.

The story of Exodus centered on a quest (back in Sosaria) to destroy the final remnant of the evil Mondain and Minax. Exodus featured revolutionary graphics for its time, being the first computer RPG to feature animated characters. Also, Exodus differed from previous games in that players now directed the actions of a party of several characters rather than just one. Players now battled groups of enemies on a separate battle screen, where the player had to understand fairly complex weapons and magic systems and employ rudimentary tactics in order to overcome each opponent, as opposed to the system in the previous two games, in which the player was simply depicted as trading blows with one opponent on the main map until either was defeated.

While previous Ultima games let the player "explore" randomly generated dungeons (in Ultima I) or poorly-designed and plotwise completely irrelevant dungeons (in Ultima II) in wire-frame first-person, Exodus' dungeons were solid-3D in appearance, integrated into the game's plot, and would remain the same across multiple plays (therefore introducing the element of requiring a player to actually create his/her own maps for dungeons). In many other ways Exodus was more focused than the earlier parts; futuristic references were largely (though not completely) gone; also there were almost no map areas that didn't serve some particular purpose in the game. The look of the game went away from being based on certain characteristics of the Apple II hardware to a carefully designed screen layout.

The game is named for its chief villain, Exodus, a demonic creation of Minax and Mondain that the series later describes as neither human nor machine. At the beginning of the game, Exodus is terrorizing the land of Sosaria from his stronghold on the Isle of Fire (later called Fire Island in Ultima Online). The player character is summoned by Lord British to defeat Exodus and embarks on a quest that takes him to the lost land of Ambrosia, to the depths of the dungeons of Sosaria to find the mysterious Time Lord, and finally to the Isle of Fire itself to confront Exodus in his lair. In the great tradition of old-school "Kill The Foozle" CRPGs, the game ends immediately upon Exodus' defeat; but unlike many games in the genre, Exodus cannot simply be killed in battle by a strong party of adventurers, but only through clever puzzle-solving and by paying attention to the many clues given throughout the game.

Although this is the last game in the series to take place in Old Sosaria, places in the game such as Ambrosia and the Isle of Fire make cameo appearances in later games, namely Ultima VII.

Exodus became a smash hit, and it is often cited as a main inspiration for later game developers.