Manny Pacquaio ran away from home at the age of 12 ... when he caught his father eating his pet dog ... this according to his trainer Freddy Roach.
Roach was talking to Yahoo! Sports about how the boxer's family struggled with poverty in the Philippines when he was a child -- and apparently, things were so tough ... Manny's father cooked the family dog for food.
When Manny realized what had happened, he ran away from home -- and began to live on the streets.
"He slept in a cardboard box. He fought his way through all this, turned pro at 14, and look at the man he is today," Roach said.
BTW -- Manny has a new dog named Pacman ... and NO ONE is allowed to eat it.