Romulan State Security was a organization in the Romulan Star Empire.

In 2374, State Security claimed they sent word of the Romulan Senate's intention to declare war on the Dominion, following Vreenak's death, to the Romulans on Cardassia. Given that many Romulans were arrested and executed, it is believed no such message was sent, or in time, to the Romulans in the Cardassian Union. (DS9 short story: "The Devil You Know")

Its possible that State Security was another name for Romulan Security.