Rocker Ozzy Osbourne is going off the rails against one of his Black Sabbath bandmates.

The “Godfather of Heavy Metal” claims guitarist Tony Iommi illegally claimed sole ownership of the band’s name, in a filing with the US Patent and Trademark Office.

Osbourne is suing Iommi for a 50 percent interest in the “Black Sabbath” trademark, along with a portion of Iommi’s profits from use of the name.

The Manhattan federal court suit also charges that Osbourne’s “signature lead vocals” are largely responsible for the band’s “extraordinary success,” noting that its popularity plummeted during his absence from 1980 through 1996.