The head of the Romulan Tal Shiar who is secretly working for Starfleet, revealed in a Section 31 operation on Romulus.
Koval is the chairman of the Tal Shiar, the Romulan intelligence service, in Inter Arma Enim Silent Leges. Section 31's Luther Sloan asks Julian Bashir to learn whether Koval suffers from the degenerative Tuvan syndrome while Bashir attends a conference on Romulus, as Koval seeks a seat on the Continuing Committee.
Koval has Bashir arrested and tortured, then exposes the supposed plot and apparently vaporizes Sloan, while Senator Cretak is convicted of treason. Admiral Ross later reveals that Koval is a Federation asset and that the true goal was to remove Cretak. Koval was played by John Fleck.