The Tal'Shiar is a secret police and intelligence organization that operates within the Romulan Star Empire. Its agents are widely feared by Romulan civilians and the regular military.
Shortly before the start of the Dominion War, the Tal'Shiar allied with the Cardassian Obsidian Order to launch a pre-emptive attack on the homeworld of the Founders. The entire plan was a trap orchestrated by a Founder who had infiltrated the Tal'Shiar, and the combined fleet was obliterated by the Jem'Hadar. The failed operation discredited the Tal'Shiar, whose influence drastically declined afterward.