The American star was best known for her role as Joanie in the hit 1970s series, and police in Indiana have confirmed that they found her dead after responding to a 911 call (via the BBC).
The cause of death is not yet known, and many fans have taken to Twitter to share their condolences.
Her co-stars Ron Howard and Henry Winkler, who played Richie and The Fonz respectively, are among them.
“Such sad sad news. RIP Erin,” Ron wrote. “I’ll always choose to remember you on our show making scenes better, getting laughs and lighting up tv screens.”
Erin’s other credits include ‘Murder, She Wrote’ and she also played Joanie in a ‘Happy Days’ spin-off, titled ‘Joanie Loves Chachi’.