The most predominant and widespread race in Barsoom, the Red Martians are virtually indistinguishable from human beings except for their red-copper skin tone and lacking a belly-button as a result of laying and being hatched from eggs. The most well know Red Martian is Dejah Thoris. Their most well known nations are Helium and Zodanga. Red Martians are very long-lived, if not completely ageless, upon reaching physical maturity they permanently hover in their age. Dejah Thoris herself was way over 400 years old when she first met John Carter, though there are exceptions such as her grandfather Tardos Mors. They are not immortal however, as they can die like any normal human being. Another natural trait they share with other Martian species is that they are naturally psychic, being able to communicate mentally with each other and and ride animals. Their gift is not advanced beyond that level, compared to other species who are capable of far more impressive feats.

The Martians' most distinguished custom is their preference of body ornaments and jewelry over proper clothing or armor. Males go into battle shirtless with minimal protection and females are practically naked, or very much close to it, to the point there is very little way of telling a princess' royal attire from that of a slave girl's. This tradition is largely attributed to Barsoom's arid enviroment (despite Mars being well-known for its cold climate) making it impossible to wear heavy clothes. Many adaptations tend to tone down this characteristic greatly, either for the sake of conservative values from the past or practicality in modern periods.

In Disney's John Carter, they are depicted as normal human beings with tattoos and markings instead of red-skin, that are supposed to represent their social standing and roles on society. Those from Helium possess red tattoos, while Zondangans have blue tattoos. They are also shown to wear modest clothing and armor.