[Photo credit: © iStock/nito100]
According to Russian news agency RIA Novosti, the 21-year-old had been taking a selfie while holding the gun to her temple.
It is understood that she accidentally pulled the trigger.
The woman, an office worker, was admitted to Sklifosovsky hospital in Moscow.
A security guard had reportedly left the 9mm gun in her office before going on holiday.
Police are investigating and have yet to make an official comment.