C-3PO (phonetically spelled See-Threepio; 3PO or Threepio for short) is a robot character from the Star Wars universe who appears in both the original Star Wars films and the prequel trilogy. He is also a major character in the television show Droids, and appears frequently in the series' "Expanded Universe" of novels, comic books, and video games. C-3PO is one of the four characters to appear in all six of the Star Wars films; the robots C-3PO (played by Anthony Daniels) and R2-D2 (played by Kenny Baker) are the only characters portrayed by the same actor in all six films.
C-3PO is a protocol droid designed to serve humans, and boasts that he is fluent in "over six million forms of communication". He is generally seen with his long-time counterpart, R2-D2. Threepio's main function is to assist etiquette, customs, and translation, so that meetings of different cultures run smoothly. Threepio and R2-D2 played a vital and pivotal role in the Galaxy's history.