Preenos was an inhabited planet that was the origin of hajjlaran, a spice.

According to space trader D'Marr, the warlords of Preenos used the spice to test their courage. (ENT: "Oasis")

This planet was only mentioned in dialogue.
According to voiceover dialogue that was scripted for ENT: "Dear Doctor" but omitted from that episode, a very similarly named planet, Pree'nos, had a Denobulan mining facility. The Denobulan miners there had attempted to make the facility look as much like their homeworld as possible. Despite this reference to "Pree'nos", the final draft script of "Oasis" spelled the planet where hajjlaran originated as "Preenos".
According to Star Trek: Star Charts (p. 60) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), there was a star system named Preenos (Rho Geminorum), in which this planet might possibly have been located, in the Beta Quadrant. This system was a trinary system with a trio of F-class stars.