Janet Hubert left The Fresh Prince of Bel-Air after Season 3. She played the original Vivian Banks, commonly called Aunt Viv, during the show’s first three seasons.
Hubert’s final season was the third, which ran from September 14, 1992, to May 10, 1993. The character remained part of the Banks family, but Hubert was replaced by Daphne Maxwell Reid beginning in Season 4. Reid played Vivian Banks for the rest of the series.
The change is sometimes described simply as a recasting, but contemporary accounts and later discussions have connected Hubert’s departure to contract negotiations and disagreements surrounding her role on the program. The recast did not remove Vivian from the story: Aunt Viv continued to be Phil Banks’s wife and the mother of Hilary, Carlton, Ashley, and later Nicky.
A common mix-up is to say Hubert left after Season 2 because Season 3 was the last one in which she appeared. Another source of confusion is the difference between the actress leaving and the fictional character leaving; Vivian Banks continued throughout all six seasons.