Gilligan (played by Bob Denver): The title character of the show, a bumbling idiot who always seems to mess up the castaways' escape. He wears a red shirt, light blue pants, and a white sailor's hat. His last name is never revealed. In the never-aired pilot episode, it is revealed that his first name is Willy.
The Skipper (played by Alan Hale, Jr.): His real name is Jonas Grumby; he is the captain of the S. S. Minnow. He is well over-weight, leading to numerous fat jokes from Gilligan. Such an instance is when the Professor and Gilligan are helping him into a wetsuit: the Skipper says that he just has big bones, to which Gilligan adds: "and they're covered in big meat."
Mrs. Howell (played by Natalie Schafer): Thurston's wife. She can be more spoiled than Mr. Howell at times, but is always the first to want to try something first. Mr. Howell always calls her "Lovey." Her name is Eunice Wentworth Howell.
Ginger Grant (played by Tina Louise): A movie star from Hollywood, she usually tries to use tricks from the movies she starred in to solve problems, causing other castaways to rescue her. She helps Mary Ann with cooking and dishwashing.
Professor (played by Russell Johnson): His real name is Roy Hinkley, and he was a high school teacher before being stranded on the island. He has numerous scientific degrees, and using his knowledge built many things on the island out of bamboo and other materials. He is the most well-learned of the group and always has a logical answer to everything (although not always correct).
Mary Ann Summers (played by Dawn Wells): A farm girl from Winfield, Kansas. Not much is said about her before getting to the island. She is portrayed as a typical "girl next door" and does most of the laundry and cooking. She is famous for her coconut cream pies, which usually end up on Gilligan's face.
Radio Announcer (voiced by Charles Maxwell): An announcer on the radio that the castaways own. The castaways would listen to his plot-advancing radio bulletins in many episodes and always with perfect timing to hear the exact news they needed to know.
Wrongway Feldman (played by Hans Conried): A fighter pilot from World War I. He was stuck on the island when he tried to fly around the world in the spirit of the Bronx. He leaves at the end of the episode, but returns later saying he will stay on the island. He leaves again however, but he crashes and never appears again. The castaways get a message from him saying he "crashed on a strange island" which appears to be Hawaii.
Dr. Balinkoff (played by Vito Scotti): A mad scientist who appears twice. For his first appearance, he takes the castaways to his secret lair on another island. In the end, the castaways escape. The second time, he uses mind-control rings to get the castaways to rob Fort Knox. He then flees when they attack him with coconuts, never to return.
Japanese Sailor (played by Vito Scotti): Appeared in two episodes. For his first appearance he locks everybody on the island up, except Gilligan and Skipper. In his second appearance, he appears in a flashback of events that never happened.
The Gorilla (played by Janos Prohaska): The only animal who acts as an antagonist on the island that causes mayhem and mischief among the castaways. In the episode "Diamonds Are an Ape's Best Friend" he kidnaps Mrs. Howell because her perfume acted as a pheromone. In the episode "Chain of Command", he disciplines Gilligan to be a better leader. In the episode "Forward March" he shells the castaways with hand grenades after he has found a stash of WWII weapons in a cave. In the episode "Our Vines Have Tender Apes", the Gorilla instead appears to resemble an orangutan.