Rules of Engagement is a science fiction novel by British write Peter Morwood.

Part of the Star Trek: The Original Series franchise, it was published by Pocket Books in 1990.

Captain James T. Kirk and the crew of the Enterprise are sent to assist in the evacuation of Federation personnel from the planet Dekkanar, which has been engulfed by civil war.

Eager to avoid getting entangled in the conflict, Kirk's orders are specifically written so that he may not even raise his ship's shields in defense.

The novel also offers an alternate explanation, via Kasak's viewpoint, of why Klingons' facial features have changed over the years.