3 Doors Down Singer Brad Arnold Dead at 47

Brad Arnold -- a founding member and the lead singer of 3 Doors Down -- has died, the band announced in a social media post.

The statement explains Brad passed away peacefully early Saturday while surrounded by his wife, other family members and loved ones following his cancer diagnosis.

The band writes Brad helped redefine rock music through his work with 3DD ... producing enduring hits over the years like "Kryptonite" -- which he penned while sitting through math class in high school.

The statement reads, "His music reverberated far beyond the stage, creating moments of connection, joy, faith, and shared experiences that will live on long after the stages he performed on."

Arnold was also a dedicated family man, the statement adds ... and, his loved ones are asking for privacy at this time.

This is the band's first post since sharing the video of Brad confirming he was diagnosed with clear cell renal carcinoma -- a form of kidney cancer -- back in May. The cancer had metastasized to his lungs ... a stage 4 diagnosis.

Arnold was the longest tenured member of 3 Doors Down ... singing and playing drums when the band first formed in 1996. He was the only member of the group to remain in the band from its inception.

3 Doors Down came out of the gates strong ... with their debut studio album "The Better Life" going seven-times platinum. Their next three albums went platinum as well.

Arnold is the second founding member of 3 Doors Down to pass away. Guitarist Matt Roberts overdosed on prescription drugs in 2016.

We last caught up with Brad in 2017 right after 3 Doors Down played President Donald Trump's first inauguration ... though he says they didn't play for political reasons. Check out why the bubbly Brad says they did play.

Arnold was 47.