The sixth season of the American ABC fantasy-drama Once Upon a Time was ordered on March 3, 2016. It debuted on September 25, 2016, and concluded on May 14, 2017. In January 2017, it was stated that the sixth season would end the main storyline, and for a seventh season, the series would be softly rebooted with a new storyline.
Existing fictional characters introduced to the series during the season include Aladdin, Princess Jasmine, the Count of Monte Cristo, Mary Lydgate, Captain Nemo, Lady Tremaine, Beowulf, Tiger Lily and the Tin Man. Original new characters include Gideon, the Black Fairy, and Robert. The show also reintroduced Jafar and Dr. Arthur Lydgate, who previously appeared in Once Upon a Time in Wonderland.
This season also marks the final appearance of Emma Swan (Jennifer Morrison) as a series regular. Morrison announced she would be departing the series after the sixth season finale, but if the series receives a seventh season renewal she has agreed to appear in at least one episode. It is currently unclear to what capacity. After serving as a series regular for two seasons, Rebecca Mader also announced that season six would be her last on the show. Shortly after, Adam Horowitz and Edward Kitsis announced that original cast members Ginnifer Goodwin, Josh Dallas, and Jared Gilmore, as well as Emilie de Ravin who joined the main cast in season two, would also exit the show at the end of the season.