Humans
- Edward Prendick – The narrator and protagonist
- Dr. Moreau – A mad vivisectionist who has fled upon his experiments being exposed and has moved to a remote island in the Pacific Ocean to pursue his research of perfecting his Beast Folk
- Montgomery – Dr. Moreau's assistant and Prendick's rescuer. A physician who enjoyed a measure of happiness in England, he is an alcoholic who feels some sympathy for the Beast Folk.
Beast Folk
The Beast Folk are animals which Moreau has experimented upon, giving them human traits via vivisection for which the surgery is extremely painful. They include:
- M'ling – Montgomery's servant who does the cooking and cleaning. Moreau combined a bear, a dog, and an ox to create him. As Prendick describes M'ling, he states that M'ling is a "complex trophy of Moreau's skill, a bear, tainted with dog and ox, and one of the most elaborately made of all the creatures". He has glowing eyes and furry ears. M'ling later dies protecting Montgomery from the other Beast Folk on the beach.
- Sayer of the Law – A large, grey-haired animal of unspecified combinations (though Edward notices its gray hair is similar to that of a Skye Terrier) that recites Dr. Moreau's teachings about being men to the other Beast Folk. The Sayer of the Law serves as a governor and a priest to the Beast Folk. He is later killed in an unseen scuffle between Montgomery, M'ling, and the Beast Folk.
- Ape-Man – An unspecified ape creature that considers himself equal to Prendick and refers to himself and Prendick as "Five Men", because they both have five fingers on each hand, which is uncommon among the Beast Folk. He is the first Beast Man other than M'ling to whom Prendick speaks. He has what he refers to as "Big Thinks" which on his return to England, Prendick likens to a priest's sermon at the pulpit.
- Sloth Creature – A small, pink sloth-based creation described by Prendick as resembling a flayed child. He is one of the more relatively benign creatures and helps Prendick kill the Hyena-Swine before fully regressing.
- Hyena-Swine – A carnivorous hybrid of spotted hyena and pig who becomes Prendick's enemy in the wake of Dr. Moreau's death. He is later killed by Prendick in self-defence.
- Leopard-Man – An African leopard-based rebel who breaks the Law by running on all fours, drinking from the stream, and chasing Prendick. The Leopard-Man is killed by Prendick to spare him further pain, much to the dismay of Dr. Moreau.
- Ox-Men – A group of gray ox-based creatures who appear twice, first when Prendrick is introduced to the Beast Folk and then again after Montgomery's death.
- Satyr-Man – A hybrid of a goat and an ape. Prendrick describes him as unsettling and "Satanic" in form.
- Swine-Men and Swine-Woman – A group of pig-based Beast Folk who appear during Prendrick's introduction to the Beast Folk.
- Mare-Rhinoceros Creature – A hybrid between a horse and a Sumatran rhinoceros who appeared during Prendrick's introduction to the Beast Folk.
- Wolf-Men and Wolf-Women – A group of wolf-based Beast Folk who appear during Prendrick's introduction to the Beast Folk.
- Bear-Bull Man - A hybrid of a bear and a cattle who appeared during Pendrick's introduction to the Beast Folk.
- Dog-Man – A Beast Man created from a St. Bernard who, near the end of the book, becomes Prendick's faithful companion. He is so like a domestic dog in character that Prendick is barely surprised when he reverts to a more animalistic form. The Dog-Man is later killed by the Hyena-Swine.
- Fox-Bear Woman – A female hybrid of a red fox and a grizzly bear who passionately supports the Law. Prendick quickly takes a dislike to her and described her as being evil-smelling.
- Wolf-Bear Man - A hybrid of a wolf and a bear who was mentioned during the hunt for the Leopard-Man as hunting his fellow Beast-Folk a wee-bit too much.
- Half-Finished Puma-Woman – The last beast-person created by Moreau. She is halfway through her process of being turned into one of the Beast Folk, but was in so much pain from the surgery that she uses her strength to break free of her restraints and escape. Moreau then chases after her with a revolver. He and the creature fight each other which ends in a mutual kill.
- Ox-Boar Man - A hybrid of an ox and a boar who appeared briefly following the death of Moreau.
- Ocelot-Man – One of the smaller creatures which briefly appears after Moreau's death and is shot by Montgomery during his scuffle with the Beast Folk on the beach.
