The girl in Luoyang, Henan province of China, had been losing her long hair and weight over the past year.
Her mother sought treatment when she discovered a lump in her daughter's stomach two weeks ago.
Doctors at the First Affiliated Hospital of Henan University of Science and Technology conducted computed tomography (CT) scans which revealed that a 30-centimetre clustered mass of hair occupied 70 per cent of the girl's stomach.
"The mass of hair was shaped like her stomach and is solid," said Chen Ye, deputy director of gastrointestinal tumour surgery department at the hospital.
The girl suffers from pica, a pathological disorder where sufferers develop an appetite for clay, dirt, chalk or other similar substances that are considered socially unusual to eat, doctors said.
"I've seen her put hair in her mouth, but I thought she was just playing and didn't think much about it," the girl's mother said.