A member of the Andorian delegation in Journey to Babel who is really a surgically altered Orion spy sent to sabotage the conference.
Thelev travels aboard the Enterprise as an aide to the Andorian ambassador Shras in Journey to Babel, as delegates make their way to the conference on Babel to debate the admission of Coridan to the Federation. Tensions are high, and when the Tellarite ambassador Gav is murdered, suspicion falls on Sarek.
Thelev attacks Kirk with a knife, wounding him, and is found to be carrying a hidden transmitter that communicates with an Orion ship shadowing the Enterprise. Kirk learns that Thelev is a disguised Orion agent sent to provoke conflict. Thelev dies from a slow poison he took before boarding. He was played by William O'Connell.