The 23-year-old, whose attack sparked protests across India, has been moved from a hospital in central Delhi to the city's international airport.
Safdarjung Hospital Medical Superintendent B.D. Athani says the victim would be flown to Mount Elizbeth hospital in Singapore with the Press Trust of India reporting that an air ambulance carrying her had left around 11.45 pm (1815 GMT).
"Based on the advice of a team of doctors, the government of India has made arrangements that the patient be shifted in a well-equipped air ambulance to a renowned hospital... so that she can be provided state-of-art medical treatment that may stretch many weeks," the doctor said.
The victim - who was attacked with an iron rod during her 40-minute gang rape on a bus on December 16 in New Delhi - was suffering from severe intestinal injuries, Dr Athani added.
"She has had to be operated upon three times," he said.
"With fortitude and courage she has survived the after-effects of the injuries so far but her condition continues to be critical."
The hospital chief hinted the student may have to receive an organ transplant in Singapore.
"The said hospital has a state-of-art multi-organ transplant facility," he said.
"The arrangement has also been made for the family to accompany her as the treatment may take longer period."
Special commission of inquiry
India earlier announced it was setting up a special commission of inquiry into the gang rape - where the woman was allegedly tricked into boarding a bus by six men who then took it in turns to assault her.
Six suspects have been arrested in connection with the attack and have been remanded in custody.
Finance Minister P. Chidambaram on Wednesday says the inquiry would "identify the lapses if any on the part of the police, or another authority or person that contributed to the occurrence, and fix responsibility for the lapses or negligence".
Mr Chidambaram also said a separate panel would examine existing legislation and "suggest changes in the laws in order to make punishment for such horrific crimes stiffer".
The panel will submit its report in 30 days.
"Whatever we do now is intended to demonstrate the government's serious intent in the matter that we will apprehend and punish the perpetrators, we will try and find out what went wrong... and fix responsibility and amend the laws," he said.
Thousands of people have taken to the streets since the attack to demonstrate both against the levels of violence and also the notoriously slow criminal justice system.
Information Minister Manish Tiwari has appealed for calm and restraint.
"It is important to underscore sensitivity and restraint from all sides is called for," he said.