The Cantrosians were a sentient race of feline beings who originated on Cantros 7. Contact with their claws could transmit Cantrosian-scratch fever. During the time of the Galactic Civil War, the Cantrosians showed strong support for the Rebel Alliance, resulting in an internal conflict after a dishonest agent attempted to manipulate groups against each other by suggesting that some Cantrosians secretly favored the Empire.
Cantrosians represented a type of cat-like humanoid lifeform. They had triangular ears, pointed teeth, small noses and whiskers, and their bodies were covered with fur. The shade of this fur varied, from gold to blue to white. The coloration of their eyes also differed between individuals, including green and orange. The species consisted of two sexes: male and female. Females had hair on their heads, sometimes with streaks. Some males also had hair, while others did not. Their claws, found on all five digits of their paws, were capable of causing Cantrosian-scratch fever. Cantrosians also wore attire such as one-piece suits and footwear.

Cantrosians were a relatively advanced civilization, capable of creating flames, flying spaceships like the T-65 X-wing starfighter, and using energy weapons. They also possessed a grasp of political concepts, with many, if not all, Cantrosians showing strong allegiance to the Rebel Alliance. Their native planet, Cantros 7, featured a main city. Some Cantrosians considered inflicting pain acceptable under certain conditions.
In 4 ABY, a male Cantrosian named Durne was employed by Nagai leader Knife—who was working to destabilize the Saijo sector for the Sith Lord Lumiya—to create conflict among his people by falsely accusing some Cantrosians of supporting the Galactic Empire, thus dividing the Rebels into opposing groups. Durne successfully completed this mission, causing each faction to leave Cantros 7 and establish bases elsewhere. Durne joined one of the groups and pretended to befriend Minka and Sami, two of its members. Minka and others were sent on a covert operation to a base in the Cantros system, where another faction had relocated.
After gathering information, the spies traveled to nearby Saijo to share their findings with their allies, but three Y-wing starfighters, piloted by Cantrosians from the other faction, pursued them, resulting in the deaths of several pilots on Minka's team. Minka survived, but her fighter was severely damaged and crashed on Saijo. Important figures of the Rebellion, Luke, Leia, and Han, happened to be on the planet and used the weapons of the Millennium Falcon to destroy the Y-wings. After Minka recovered, the Rebellion heroes took her to Saijo, where she introduced them to the other Cantrosians in her faction. Minka and Sami decided to retaliate, but Durne, wanting to maintain his deception, created a false explanation and secretly went to the enemy base.

As the group traveled in the Millennium Falcon toward the opposing faction's planet, they were attacked by more enemy Y-wings, forcing the Falcon to land in a ravine on an asteroid. Sami, Solo, and Skywalker were captured by the Cantrosians there, while Minka and Organa escaped. At the base, Sami and his companions were threatened with torture, but the faction's leader, Niru, refused, stating that torture was an Imperial practice, revealing her faction's true allegiance. Durne then appeared and worsened the situation by encouraging Niru to torture their captives. An angry Sami, along with Solo, exposed Durne's betrayal and assured Niru that they were also Rebels.
Minka and Organa arrived and disarmed Durne, which led to a battle when the faction mistook the two for potential Imperials. Niru refused to fire and tried to de-escalate the situation, but Durne, believing that Niru's death from an 'unknown source' would restore his control, attempted to attack her by surprise. Skywalker activated his lightsaber and deflected Durne's shot, incapacitating him. Witnessing this, the Cantrosians realized the truth of the deception. While Solo explained the misunderstanding, Durne tried to escape, but Niru caught him. With the conflict resolved, the Cantrosians agreed to return to Cantros 7 and live together peacefully. They took Durne with them, intending to uncover the truth through fair interrogation.
At least two Cantrosians were present on the central planet of Coruscant in 19 BBY. After scolding a Herglic for bumping into him, Sullustan journalist Den Dhur noticed the pair and thought he should have been more polite, due to the risk of contracting Cantrosian-scratch fever if he upset them. One elderly female Cantrosian lived on Malastare as of 1 BBY, where she sold pashi noodles from a street vendor. Juno Eclipse, an Imperial pilot who later joined the Rebellion, was one of her customers.
The Cantrosian species was first seen in the 1984 Marvel Comics issue Star Wars (1977) 93, illustrated by Sal Buscema and colored by Petra Scotese. Their name was given in Michael Reaves' 2008 novel Coruscant Nights II: Street of Shadows.