The secretive interstellar empire of the Romulans, ruled from Romulus and for centuries a rival of the Federation.
The Romulan Star Empire is the state founded by the Romulans, offshoots of the Vulcans who left their homeworld long ago and settled the twin worlds of Romulus and Remus. It is ruled by a praetor and the Romulan Senate, and its intelligence service, the Tal Shiar, is feared even by its own citizens.
Earth fought the Earth-Romulan War against the empire in the 22nd century, and the conflict ended with the creation of the Romulan Neutral Zone. The Treaty of Algeron in 2311 renewed the border and barred the Federation from developing cloaking technology, and the Romulans spent long periods in isolation.
The empire joined the Dominion War on the Federation's side in 2374 and suffered heavy losses. In 2387 the supernova that destroyed Romulus shattered the empire, leaving successor states and scattered refugees in the era of Picard.