Along with the Simpson family, The Simpsons includes a large array of characters: co-workers, teachers, family friends, extended relatives, townspeople, local celebrities. The creators originally intended many of these characters as one-time jokesters or for fulfilling needed functions in the town. A number of them have gained expanded roles and subsequently starred in their own episodes. According to creator Matt Groening, the show adopted the concept of a large supporting cast from the Canadian sketch comedy show Second City Television.

The main episode characters, the Simpson family, are listed first; all other characters are listed in alphabetical order. Only main, supporting, and recurring characters are listed. For other recurring characters, see List of recurring The Simpsons characters.