Mirhassa was a planet in the Romulan Star Empire, described as a "distant outworld".
In the 2220s the Imperial government forcibly relocated Kaveth Ship-Clan from Remus' south-tropical continent to Mirhassa and Ssuvat, among other worlds, to isolate them from other political dissidents. The Kavethssu smuggled out a number of plants from their homeworld, including the plant from which tivish fabric was produced, and began smuggling it back to Romulus and Remus. (TOS - Rihannsu novel: The Empty Chair)