Tragic news from Conor McGregor -- the UFC superstar's beloved dog, Hugo, has passed away.
Conor gave a heartfelt goodbye to his four-legged friend minutes ago ... saying, "So heart broken to say my dog Hugo has passed away."
McGregor reflected on the memories he shared with the mixed breed for so many years ... dating back to the days before he became a household name in the MMA community.
"He was with me all the way, my closest companion.