Thomas More
the author of Utopia. He is a character in his own work. In the opening letter to Peter Giles, More explains that he is writing a record of a conversation that he and Giles had with a man named Raphael Hythloday. More does not do much speakingHythloday is the main speaker. In the opening and closing letters to Peter Giles, More reveals aspects of his character. More is very clever and he makes several jokes and puns in attempts to be humorous. In the closing letter to Giles, More makes it clear that Utopia is a fictional place that does not actually exist.
Peter Giles
a friend of the author, Giles was a printer and editor, also serving as the Clerk of Antwerp. In Utopia, Giles meets More when the Englishman travels to Flanders (present-day Belgium). Giles introduces More to Raphael Hythloday and Utopia is a narration of Raphael's words to Giles and More.
Raphael Hythloday
a fictional character. Though Giles and More are actual people, Hythloday is entirely fictional. Raphael is the name of a Biblical angel but the name Hythloday means "peddler of nonsense." Hythloday brings good news of the ideal society, found on the island of Utopia. Unfortunately, the island does not exist. Hythloday is a Portuguese man who sailed on the fourth voyage of Amerigo Vespucci. Vespucci was actually a sailor and discover (after whom America is named).
Hythloday is the main character in Utopia and he is distinct and unique from the others. Hythloday is very wordy and he speaks in long sentences. It's difficult for the other characters to get a word in edgewise. At the same time, Hythloday tends to be pretty dogmatic in his views. He is an absolute fan of Utopia: he praises all of their customs, criticizing nothing. Hythloday can seem very sensible at times, despite his ridiculous traits. In discussing court politics, Hythloday is wiser than More, realizing that the fickle shifting views of a king's flattering advisers can make the court an unpleasant adventure for the well-intentioned honest adviser. More rejects Hythloday's advice and learns his lesson the hard way.
Utopus
the ancient conqueror who built the Utopian state. 1760 years before Hythloday's visit to Utopia, Utopus conquered the brutish people and separated the area into its own island by cutting through the narrow isthmus that connected Utopia to the mainland. Most of the laws, institutions, and values passed down by Utopus remained in place 1760 years later, when Raphael visited.
Source: http://www.gradesaver.com/utopia/study-guide/character-list/