Technology of Romulan origin, first described in 2266, that can generate an energy screen to render a target object — usually a spacecraft — relatively invisible to sensors.

Due to their immense power drain, cloaking generators have usually prohibited simultaneous use of other major systems such as weaponry, shields or warp drive.

Although common to Klingon ships as well since the short-lived alliance with Romulus in the 2260s, Federation vessels have agreed to forego use of cloaks under the Treaty of Algeron, except in the case of the U.S.S. Defiant, which utilizes such a device by special arrangement.