The Reman Viceroy was the title of Praetor Shinzon's Reman adviser, Vkruk, during the Remans successful coup of the Romulan Star Empire's government. He served as Shinzon's lieutenant and helped him cope with his sickness through a form of telepathic healing though this only eased the pain. It is uncertain whether this title would have remained had Shinzon remained as Praetor or if the Reman government has adopted the title for its head of state. (movie: Star Trek Nemesis)
History of character is unknown.
The term Viceroy could apply to a variety of governing positions, often in place of a monarch or in control of a large jurisdiction.
The leader of the Trade Federation would hold the title of Trade Federation Viceroy, the most historically notable being Nute Gunray. Another example of Viceroy was the Darama, leader of the Yevetha and Head of State of the Duskhan League. Viceroy was also one of the titles, the other being First Chairman, held by Bail Organa.