In the fictional Star Trek universe, the Medusans are a highly intelligent, noncorporeal species and member of the United Federation of Planets. Their first appearance was in the Star Trek: The Original Series episode Is There in Truth No Beauty?.

It is interesting to note that the Medusans are one of, if not the only, noncorporeal beings that are active members of the Federation. Because of their different structure and correspondingly different sensory systems they are much better suited for space travel then most members of the Federation. However, it is very difficult for the Medusans to interact in a meaningful way with the mostly humanoid Federation. This is due to the fact that the Medusans have not completely shed their physical form and must always have it with them. This physical form is said to be so hideous that a humanoid viewing it without protection will be driven insane. An interesting side note is that while the Medusans body is grotesque in the extreme, their advanced mind - when viewed by those with telepathic abilities (i.e., Betazoids) - appears to be quite beautiful.