Tilonus IV was the fourth planet in the Tilonus planetary system. This was the homeworld for the Tilonians, a highly advanced humanoid species.

During the 2360s, the government of Tilonus IV was in a condition of total anarchy when Commander William T. Riker attempted to rescue a Federation research team there in 2369. He was captured by one of the factions and subjected to neural manipulation by Suna at the Tilonus Institute for Mental Disorders in an attempt to extract tactical information from him. (TNG: "Frame of Mind")