The Benthans are a warp capable species from Benthos in the Delta Quadrant.
Physically, they are humanoid with a large nasal structure that extends up to their foreheads.
They were encountered in 2374 when the USS Voyager met the Benthan test pilot, Steth. He was flying an experimental ship equiped with a Coaxial warp drive.
In fact, a shapeshifting alien had switched places with the real Steth some time earlier. The alien switched again with Tom Paris and later with Kathryn Janeway before being apprehended. (VOY: "Vis a Vis")
- It is possible that the Coaxial warp drive belonged to the alien and not to the Benthans. However this is unlikely as the alien abandons the ship when he takes over Tom's body.