The Mengenites were a civilization native to the Mengen star system in the Alpha or Beta Quadrant, in the vicinity of Sol in Federation space in the 23rd century.

The Mengenites were a sovereign group that were not a member of the Federation by the year 2270. Commander Paul Burch of Starfleet feared that the power schemes of Vice Admiral Vaughan Rittenhouse were a threat to sovereign civilizations like the Mengenites. (TOS - Fortunes of War novel: Dreadnought!)

Representatives of the Mengenite species were space travelers, known to frequent spaceports throughout local space, including Federation open ports on planets such as Argelius II. A pair of Mengenites were among an audience to a belly-dance preformed by Lieutenant Commander Piper of Proxima Beta, who was attempting to investigate illegal research performed by visitors to Argelius. (TOS - Fortunes of War novel: Battlestations!)