The Rigelian language was a language spoken and written by the Rigelians.
It was used by the operators of the trade complex on Rigel X, and was used in signage of the Central Security offices. (ENT: "Broken Bow")
A deleted scene from this episode would have established that the language used a pronominal base.
Hoshi Sato could understand Rigelian, but was knocked unconscious before she could make out what a pair of Rigelian kidnappers were saying about their plot to kidnap Doctor Phlox. (ENT: "Affliction")
During the Coalition of Planets negotiations in 2155, the universal translators experienced a "glitch" and started confusing the Rigelian language with Andorian. Minister Nathan Samuels later reported this fact to Captain Jonathan Archer. (ENT: "Terra Prime")
Doshat tiyung nevreel.
"Bring him with us."
- - Kidnappers, regarding Dr. Phlox. (ENT: "Affliction")