Main characters
- Gilligan (portrayed by Bob Denver) – As the sitcom's title character, Gilligan is the first mate (and sole crewman) of the S. S. Minnow under the Skipper. He's well-meaning and incompetent in roughly equal measure. Gilligan frequently and inadvertently messes up the castaways' efforts to get themselves rescued; moreover, he is typically blamed for said failures whether he's at fault or not. He wears a red shirt, light blue pants, and a white sailor's hat. His first name is never mentioned in the original run of the show, or any other movies/cartoons. When promoting the first reunion movie on Dick Cavett's show, it was asked if Gilligan was his first or last name. Sherwood Schwartz replied that it was never stipulated, but obviously sounded like a last name. Bob Denver said he always felt like Gilligan's first name should be Willie and Sherwood Schwartz agreed.
- Cpt. Jonas Grumby (portrayed by Alan Hale Jr.) – Referred to in the series as "The Skipper" (but often as "Captain" by Mr. Howell), who is the captain of the S. S. Minnow. His portliness leads to numerous fat jokes, mostly 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". The Skipper is just slightly more able-minded than Gilligan, with whom he has a love-hate relationship: he'll often address his first mate as "Little Buddy", then get frustrated and swat Gilligan in the head with his hat. Basically, he plays Oliver Hardy to Gilligan's Stan Laurel.
- Thurston Howell III (portrayed by Jim Backus) – Thurston is a millionaire used to luxurious living and never does any work on the island. The only exception is when the castaways believe that Mr. Howell is broke and make him work. He devises many get-rich-quick schemes on the island. Thurston was originally a multi-billionaire until the stock market crash rendered him a multi-millionaire.
- Eunice "Lovey" Howell (portrayed 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 new. Mr. Howell always calls her "Lovey". Her maiden name is Wentworth.
- Ginger Grant (portrayed by Tina Louise) – A Hollywood movie star. Ginger usually tries to use tricks from the movies she starred in to solve problems, causing other castaways to rescue her from any dangers that befall her. She helps Mary Ann with cooking and dishwashing.
- Roy Hinkley, Ph.D. (portrayed by Russell Johnson) – Referred to on the series as "The Professor", he was actually a high school teacher and scout master before being stranded on the island. He has numerous scientific degrees and uses his knowledge to build many things on the island out of the available materials.
- Mary Ann Summers (portrayed by Dawn Wells) – A farm girl from Winfield, Kansas. Not much is known about her before she gets to the island. She is portrayed as a typical "girl next door" and does most of the laundry and cooking with some help from Ginger.
