A 16-year-old student in Class 1-F at Furinkan High School. He has a unique constitution where he turns into a girl when splashed with cold water and returns to a boy with hot water. Though Japanese, he usually wears Chinese-style clothing due to his time spent training in China. While he wears various outfits throughout the series, his favorite is reportedly the red kung fu shirt he is most often seen in. He is frequently noted for his good looks, taking after his mother rather than his father, Genma. Furthermore, in his female form (Ranma-chan), he possesses a physique that surpasses even Akane's, and it is revealed as the story progresses that his bust size actually increases. Due to his attractive appearance, he is often pursued by the opposite sex, though he has a tendency to attract eccentric and troublesome individuals. His martial arts skills are top-tier among the main cast. While his masters, Genma and Happosai, have questionable character, they are peak-level grandmasters; by constantly clashing with them, Ranma has become a first-rate martial artist himself. Additionally, he has trained under Cologne, another top-level master, giving him an exceptionally privileged environment for a warrior. As a result, he is usually one step ahead of Ryoga, Mousse, and Tatewaki Kuno, who largely hone their skills through self-teaching. His ultimate goal is to become the world's strongest martial artist and inherit the Anything-Goes School of Martial Arts. However, since Happosai is so irresponsible, the specifics of this goal remain somewhat vague by the end of the series. Since Genma and Soun declined the position, there are no other candidates besides Ranma, so the succession is likely secure. He is skilled at sports in general and is a talented cook. He is dexterous and can handle almost any physical task with ease. His favorite foods are okonomiyaki and takoyaki. He also has a sweet tooth for parfaits; he often transforms into his female form to have Akane accompany him to cafes, much to her exasperation. His weaknesses are cats and gambling. Cats, in particular, are his greatest weakness due to reckless training he was forced into as a child; he hates them so much he panics at the mere touch of one. The cause was his father, Genma, tying fish cakes to young Ranma and throwing him into a pit of hungry cats. When his fear of cats reaches its limit, he enters a state called the "Cat Fu" (Neko-ken), where he begins to act and fight like a cat himself. He constantly boasts that he has never lost a fight involving martial arts, though he usually loses once before winning the rematch. It seems Ranma is referring to his record in "official matches." He is extremely sore loser, but this is also the source of his strength; when seeking a rematch, he shows an obsession that involves exhausting every possible effort and strategy. As Akane put it, "He's the type who absolutely never gives up until he wins." Like a typical high school boy, he is a big eater and can be a bit greedy when it comes to food.

Ranma Saotome after being splashed with cold water. His way of speaking remains basically the same.

Ranma's fiancée, decided by their parents without their consent. She is a cheerful girl with no hidden agenda and a very strong sense of justice. While she appears tomboyish at first glance, she has a kind side. Her main flaw is her terrible cooking.