An interspecies conflict or interspecies war was a conflict between members of different species.
In 2151, Maxwell Forrest cautioned Jonathan Archer about getting Earth involved in an interspecies conflict between Vulcan and Andoria. (ENT: "Sleeping Dogs")
In 2380, Carol Freeman was angry about potentially having to explain to Starfleet Command why the Rat-lizard homeworld was experiencing an interspecies war after being at peace. (LD: "Crisis Point")