This article is about hypothetical inhabitants of Mars. In computer networking there are also "Martian packets," and a group of famous physicists and mathematicians from Hungary were dubbed "The Martians"

The name Martian is given to the hypothetical native inhabitants of the planet Mars. Historically, life on Mars has often been suggested, and the notion continues into the present day, having such proponents as Courtney Brown. While it remains possible that there is life on Mars, it is currently doubted by the scientific community.

The idea of intelligent Martians was popularized by Percival Lowell and in fiction, especially by H. G. Wells' War of the Worlds and Edgar Rice Burroughs' Martian Chronicles. Despite the observation by Alfred Wallace that Mars' atmosphere was too thin to support an Earthlike ecology, various depictions of a Martian civilization were popular throughout the twentieth century. The first pictures of Mars returned by space probes dashed hopes of contacting Martians, although dubious claims of past Martian civilizations continued into the twenty-first century. (See face on Mars for one such claim.)

Because of the prevalence of stories containing Martians, the idea of 'Martian' has become the default identity of extraterrestrial characters in popular culture.

If Mars is one day colonized by humans, the generations descended from the settlers will most likely also be called Martians. Some members of the Mars Society, an organization devoted to such colonization, semi-humorously describe themselves as 'Martians in exile'.

For various descriptions of fictional Martians, see Mars in fiction. For discussion on the possibility of Martian micro-organisms, see extraterrestrial life.