My Enemy, My Ally is a science fiction novel by American writer Diane Duane, part of the Star Trek: The Original Series saga.

She convinces her crew to cross the Neutral Zone into Federation space, where the Enterprise is patrolling with the Starships Constellation, Intrepid and the Denebian Defender-class battleship Inaieu.

The Captain declines, but when the USS Intrepid mysteriously vanishes during an ion storm, Ael convinces him that the ship has been captured by Romulans and its Vulcan crew will become part of the project.

The plan involves Ael's ship pretending to capture the Enterprise, taking it back home through the Romulan defences on a course which will pass close to the research station.

The plan proceeds smoothly until a double cross by Ael's son, Tafv, threatens to leave the Enterprise genuinely captured.