The Lorillians were the natives of Lorillia, a member world of the United Federation of Planets prior to its destruction by the Borg in 2381.(ST novel: Lost Souls) Young Lorillians breathed methyl oxide for the first few years of their life, and had to be "weaned" onto oxygen.

The Lorillians were a species the Klingons dealt with, through Ambassador Kage, at some point prior to 2311. (TLE novel: Serpents Among the Ruins)

The Lorillians suffered terrible losses when planet Lorillia was destroyed in the Borg Invasion of 2381.