"Unification" is a two-part episode of the syndicated American science fiction television series Star Trek: The Next Generation which features Leonard Nimoy as Spock. The first of the two episodes earned a 15.4 household Nielsen rating, drawing over 25 million viewers, making it one of the most watched episodes in all seven seasons of The Next Generation's run.

Set in the 24th century, the series follows the adventures of the Starfleet crew of the Federation starship Enterprise-D. In this episode, Picard is in search of ambassador Spock who may have defected to the Romulan Empire.

This episode has been praised for the "novelty and nostalgia" of seeing Spock, and noted for introducing a peace-loving Romulan faction.

Story elements and appearances by Spock are included in "Unification III" in Star Trek Discovery.