A Royal Air Force plane sent to the west African country yesterday is bringing the military servicewoman back to be treated in London's Royal Free Hospital, an MoD spokeswoman said.
The condition of the patient, who was publicly confirmed to have Ebola yesterday, is unknown.
She is the third Briton to contract the virus in Sierra Leone -- two nurses, William Pooley and Pauline Cafferkey, recovered after being treated in Britain.
Ebola has swept through Sierra Leone, Guinea and Liberia since December 2013, killing more than 9,900 people, according to the World Health Organisation (WHO).
The MoD spokeswoman said: "Despite there being stringent procedures and controls in place to safeguard UK service personnel, there is always a level of risk in deployments on operations of this type."
Public Health England, a government agency, has said that the risk to the British public was "very low".
