Isabel Gayther, 21, was located at an address in north London on Thursday five days after a disappearance the Metropolitan Police described as "extremely out of character".
Officers had seen and spoken with Ms Gayther and were "satisfied that she is safe and well", Scotland Yard said.
Relatives raised the alarm after she did not turn up at the family home in Oxford on Christmas Day.
Police in Lewisham had appealed for the public's help to trace the student, who lives in halls of residence on Goodwood Road in New Cross, south-east London.
She had not been seen or heard from since about 11.30am on Christmas Eve but messages had been posted on her Facebook account two days later suggesting she was fine.
A message posted on her account said: “Am not on my way to Syria or being held hostage.
“A day and half I'm out of contact and this is what happens??? I AM NOT MISSING peace."
It added: “How embarrassing, this is the second time my mum has filed a missing persons report, for a missing person I just keep coming back...
“Now I look like a c***.”
Scotland Yard thanked the media and the public for their assistance.
