The fourth season of the American science fiction television series Star Trek: Voyager commenced airing on UPN in the United States on September 3, 1997, and concluded on May 20, 1998, after airing 26 episodes. Set in the 24th century, the series followed the adventures of the Starfleet and Maquis crew of the starship USS Voyager after they were stranded in the Delta Quadrant, far from the rest of the Federation. Season Four featured the debut of new main cast member Jeri Ryan as Seven of Nine, nicknamed Seven, and the departure of Jennifer Lien, who portrayed Kes during the first three seasons of the show. At the end of the season, co-creator and executive producer Jeri Taylor retired.

Kes is a fictional character played by Jennifer Lien on the American science fiction television show Star Trek: Voyager. She is a member of a telepathic alien species known as the Ocampa who have latent psychic abilities and a life span of only nine years. Joining the starship USS Voyager's crew in the pilot episode "Caretaker", she opens a hydroponics garden and works as the medical assistant to the artificial intelligence known as the Doctor. Her storylines focus on encouraging the Doctor to develop his humanity and dealing with her Talaxian boyfriend Neelix's jealousy. She also seeks to expand upon her mental capabilities, leaving in the fourth season after her powers threaten to destroy the ship. She reappears in a season six episode and features in Star Trek: Voyager novels and short stories.