Morfin Gaunt is a fictional character from the Harry Potter Universe.
He is the son of Marvolo Gaunt, and is the uncle of Voldemort. He is described as a mix between dumb and mad.
Morfin is seen in a memory which Dumbledore has aquired from a Ministry man. While he appears to be quite dumb, his father is a little smarter. The Ministry man, named Bob Ogden, later arrested both of them. Morfin got a longer punishment than his father, and when his father returned to home, his daughter - Morfin's sister - had gone away with Tom Riddle Sr.. Marvolo couldn't even cook his own meals, so he died shortly after.
When Morfin was released, he was approached by Voldemort. Morfin then told Voldemort about his parents. Voldemort's mum was already dead, but his father was still alive. Voldemort travelled to the Riddle mansion and killed his father and grandparents. He next made Morfin believe he had killed the Riddles. Again, Morfin was sent to Azkaban, and he died before he was released.