WWE Superstar Sheamus Mourns Dog's Death, 'You Stole My Heart'

WWE Superstar Sheamus just shared some heartbreaking news ... announcing the death of his dog, Betty -- just weeks after she completed her last round of chemo.

The Grand Slam Champion mourned the devastating loss in a lengthy Instagram post on Wednesday ... saying the past few years were incredibly special with her in his life.

"Even though our time together was cut far too short, I'll never regret the decision to make her part of our family. She brought so much joy and happiness into our home and into the lives of everyone who met her," Sheamus said.

He admitted the moment he laid eyes on "this chunky little pup" at the National Humane Association, there was no questioning whether he'd leave her behind.

"Even after losing her leg, she never lost her spirit -- she was still just as happy, just to be home, surrounded by love. You stole my heart, and the hearts of everyone who knew you."

His wife -- Isabella Revilla -- shared her own tribute to Betty on Instagram ... saying she passed away at their home in Nashville.

"She was the happiest, sweetest, silliest girl until the very end," Revilla said. "Cancer took her leg and more but it never took her spirit."

The comment section was flooded with fans and other wrestlers sending their condolences.

"Love you bud," CM Punk wrote. "Big hug when I see you next."