Kottak's daughter, Tobi, tells us ... her father passed away Tuesday morning in Louisville, KY -- although further details about the exact circumstances weren't immediately available. Metal Sludge first reported rumblings of the musician's death.

His exact cause of death is unknown as of yet.

James is best known for being in the hard rock German band Scorpions ... joining the group in 1996 and becoming their longest-serving member until he was fired in 2016 for his alcoholism.

He had spoken of his battle with booze over the years ... saying in October 2022 he hadn't been able to completely ditch alcohol and it was an ongoing process.

Before that, he was well known for being the original drummer for Kingdom Come ... who made a significant impact in the '80s thanks to their Led Zeppelin-style music.

He also toured in other bands such as KrunK, Montrose, Wild Horses, and Buster Brown, among many others.

Alongside music, James made some reality TV show appearances -- most notably in 2012's "Ex-Wives of Rock."

He was famously married to Tommy Lee's sister Athena from 1996 to 2010 ... with a bitter custody battle ensuing over their son Matthew.

He was 61.