Which Seinfeld episode introduced Festivus to viewers?

“Which Seinfeld episode introduced Festivus to viewers?” — “The Strike” introduced Festivus to television audiences.

The Season 9 episode centers on George’s father, Frank Costanza, and the unconventional holiday he celebrates on December 23. Its traditions include an unadorned aluminum pole, the airing of grievances, feats of strength, and “Festivus miracles.”

Festivus was not invented entirely for the sitcom. Writer Dan O’Keefe adapted it from a quirky holiday created by his father, author Daniel O’Keefe, whose family had celebrated a private version years earlier. The show transformed that personal custom into a memorable piece of pop culture.

Viewers sometimes call the episode “The Festivus,” but its official title is “The Strike.” It originally aired on December 18, 1997, and the holiday’s popularity expanded dramatically after the episode.