Tom Phillips leapt into action when the enormous Limousin bull - weighing in at 2,000lb - threw his dad Andrew in the air and began to attack him.
Andrew, 46, and Tom had been tending the cattle when the bull unexpectedly charged.
Quick thinking Tom jumped into their Massey Ferguson tractor and steered it towards the bull to nudge it away from his dad, who he thought was dead.
The plucky youngster - who had never driven the tractor before - then raced home to his mum Amanda, screaming 'Dad's dead! Dad's dead!'
Amanda, 39, ran to the scene and after failing to find a pulse on her husband, phoned 999.
An RAF rescue helicopter flew Andrew from the family's farm in Abergavenny, South Wales to hospital.
He had suffered ten broken ribs and severe internal injuries, but now recovering at home.
Brave Tom told reporters:
"I was a bit worried about driving the tractor but I just did what I had to do."
WOW! What a brave boy!