Police have arrested a man, 25, on suspicion of murder after his mother was found dead at her home in Upper Ngau Tau Kok Estate.
Officers said the woman, 50, had not been seen for a few days.
A nurse went to check on her on Wednesday afternoon, and although she heard noises inside the flat in Sheung Wing House, nobody answered the door.
Firefighters then broke into the unit, police said.
Officers said the woman, whose body was found in a bedroom, had numerous bruises and scratches on her face, back and arms.
Police also said the suspect has a history of mental illness.