The Klingon-Reman Protectorate was a region of space that was under a protectorate status by the Klingon Empire.
This consisted of Reman territory namely Remus itself and Ehrie'fvil on Romulus. The protectorate came into existence after Shinzon of Remus's death and during the Reman uprising which was being led by Colonel Xiomek. Rather then see an all out war breaking out btween the Romulans and their former slaves, Captain William T. Riker of the USS Titan managed to convince the Reman allies, the Klingons, to serve as their protecters.
This act brought about the creation of the Klingon-Reman Protectorate and was administered by newly promoted governor Khegh. The creation of the protectorate infuriated the Romulans who saw it as a beach head for the Klingons into the heart of the Romulan Star Empire but were forced to accept the terms of the agreement due to internal political problems. (TTN novel: The Red King)