Joe Negri, famous for playing the musical handyman on "Mister Rogers' Neighborhood," is dead.

Joe's death was announced Sunday, just days before he was set to celebrate his 100th birthday ... according to multiple reports.

The official cause of death is unclear ... though his daughter reportedly said he died Saturday from natural causes.

Joe was known as Handyman Negri on the long-running children's classic ... for 30 years he played music and fixed things alongside the puppets of the Neighborhood of Make-Believe.

As the show progressed and Handyman Negri became a fan favorite, he eventually had his own "Negri's Music Shop" in Mr. Rogers' neighborhood ... playing jazz guitar with the likes of Yo-Yo Ma, Wynton Marsalis and Johnny Costa ... among others.

Handyman Negri was 99.

RIP