Thonolan IV is the fourth planet in the Thonolan system. It is home to a large Andorian colony, and is run by an "Administrator".

During the 2360s, Thonolan colony was run by Administrator Thuvat.

The Andorian Ambassador to the Federation, Thev, and his blind daughter Thala lived on the planet until the mid-2360s. Thev was being transported to another planet by the Enterprise-D, when it was catapulted 8,000 lightyears away by Q. When a strange, and then new species called "The Borg" sliced a piece of hull out of the Enterprise, Thev was killed, and Thala was orphaned. (TNG episode: "Q Who?")

Dr. Selar, a Vulcan medical practitioner aboard the Enterprise adopted Thala, as people with disabilities were frowned upon in the Andorian culture. (novel: "The Eyes of the Beholders")