Tyson Fury -- one of the toughest fighters on the planet -- is showing off his softer side by releasing a cover of one of his favorite songs ... and it's for a really good cause!!
The heavyweight boxer just delivered his own rendition of Neil Diamond's 1969 classic hit, "Sweet Caroline" ... and we gotta admit, it's solid!!
The 34-year-old -- along with background singers -- hit every note on the track ... including the iconic chorus, "Sweet Caroline, good times never seemed so good!