Police said a emergency team in Indiana responded to a call on Saturday afternoon and found her dead.
The cause is not yet known.
Moran also starred in the show's spin-off series Joanie Loves Chachi, which began in 1982. She played Joanie Cunningham, the younger sister of lead character Richie.
Richie was played by Ron Howard, who has been among those posting the first tributes online.
Henry Winkler, who played The Fonz in the series, also shared condolences on Twitter.
