The Sentinel, an Interdictor type of cruiser, served the Galactic Empire's Imperial Navy during the campaign led by Grand Admiral Thrawn against the New Republic in 9 ABY. In the Battle of Bilbringi, the Sentinel, along with Interdictor cruisers such as the Constrainer, was strategically positioned to halt the incoming flotilla of the New Republic, allowing other Imperial forces to engage. After the Interdictors extracted the New Republic ships from hyperspace, Thrawn ordered both the Constrainer and the Sentinel to rejoin the main Imperial battle line. The battle concluded with Thrawn's death at the hands of his bodyguard, Rukh, resulting in an Imperial withdrawal.
The 1991 novel The Last Command, the final book in Timothy Zahn's Star Wars: The Thrawn Trilogy, marked the first appearance of the Sentinel. The novel identifies the Sentinel as an "Interdictor Cruiser." The Dark Force Rising and The Last Command comics depict these ships in various forms, either as Immobilizer 418 cruisers, like the Constrainer, or as Interdictor-class Star Destroyers.
Within the 2006 strategy game Star Wars: Empire at War, Sentinel can be a name that the game gives to Immobilizer 418 cruisers constructed by the player controlling the Imperial forces.