EXCLUSIVE

The youngest "Partridge Family" star Suzanne Crough died Monday at her home in Nevada ... TMZ has learned.

Crough starred as the tambourine-shaking daughter Tracy Partridge ... during the classic sitcom's run from 1970 to 1974.

She was 52 years old. It's still unclear what caused her death, but a family member confirmed Suzanne's passing and said it was sudden.

Suzanne was married with 2 daughters ... one of whom is getting married this summer.

She last reunited with her 'Partridge' co-stars for an appearance on the 'Today' show back in 2010.

David Cassidy tells TMZ he was saddened to hear about the sudden passing, adding, "Although, we did not know each other very well due to our age difference during our Partridge days, I always thought fondly of Suzanne and her family."