By Agence France-Presse
The girl was air-lifted to hospital after being bitten on the leg while swimming in the Whitsundays in northeastern Australia, first responders said.
"Paramedics are treating a female child in a serious condition with a significant leg injury," Ambulance Queensland said, without providing further details.
The incident occurred within 24 hours of an attack on a Tasmanian women in the same area.
The 46-year-old remains in a critical condition after being bitten on the upper left leg, in what witnesses described as a horrific ordeal.
"I just saw this yacht anchor about 60 metres off my boat, there appeared to be six people on board and they all seemed to be laughing and all that," witness Mark Yates told national broadcaster ABC.
"Twenty minutes later there was this screaming and I thought 'geez, they seem to be having fun', and then the screaming kept continuing and I got up to have a look and I saw them dragging the poor woman out of the water," he added.
"There was blood everywhere."
Experts say shark attacks are increasing as water sports become more popular and bait fish move closer to shore, but fatalities remain rare.
Local authorities have reportedly warned holidaymakers and locals not to swim in the area.
The Whitsundays is an island chain featuring pristine beaches, turquoise water and sparkling reefs on Queensland's tropical coast.
The area is popular with tourists from all over Australia as well as visitors from overseas.