Yesterday's Enterprise

"Yesterday's Enterprise" is the 63rd episode of the American science fiction television series Star Trek: The Next Generation. It is the 15th episode of the third season, first airing in syndication in the week of February 19, 1990. Set in the 24th century, the series follows the adventures of the Starfleet crew of the Federation starship Enterprise-D. In this episode, the ship's crew must decide whether to send the time-travelling Enterprise-C back through a temporal rift to its certain destruction, to prevent damaging changes to their timeline.

The plot for "Yesterday's Enterprise" was based on the merging of two story ideas—one featured the crew of the time-traveling Enterprise-C and the other the return of Denise Crosby, whose character Tasha Yar had been killed in the series' first season. Trent Christopher Ganino and Eric A. Stillwell rewrote the merged story to feature the character of Guinan more prominently. To complete the episode in time for sweeps, the final script was finished by a team of five writers.

Filming of the episode lasted a week, with some elements of the script ultimately not included due to time constraints. In syndication, "Yesterday's Enterprise" outperformed most of the third season's episodes with a 13.1 Nielsen rating, the third-highest number for the series at the time. The episode is cited as a favorite by crew members and reviewers, and is widely regarded as one of the best episodes of the series.