The patient, who is a healthcare worker, is to be treated in an isolation unit at the Royal Free Hospital in north London.
Health chiefs say the risk to the UK from the virus remains “very low”.
The patient, who is not “seriously unwell” according to the Department of Health, is the first Briton to have contracted the virus in an outbreak that has killed at least 1,427 people in West Africa since March.
Flanked by a police escort, a special military ambulance took the man across London to Britain’s only specialist Ebola isolation unit at the Royal Free Hospital.
His bed will be sealed off with a tent with its own ventilation system, and only specially trained staff can enter the unit.
A spokesman for Sierra Leone’s health ministry, Yahya Tunis, said the man was a volunteer nurse working in Kenema in eastern Sierra Leone, one of the areas hardest hit by Ebola which has now been quarantined.
He caught the virus while caring for patients at a hospital where 15 nurses have already died of the disease.
“His colleagues are very sad over the development as he is considered as a valued member,” Tunis said, adding that he was involved in “surveillance, contact tracing and the burial of Ebola victims”.
England’s deputy chief medical officer Professor John Watson insisted that the risk of the virus being spread in Britain remained “very low”.
“UK hospitals have a proven record of dealing with imported infectious diseases and this patient will be isolated and will receive the best care possible,” he added.
Ebola spreads through direct contact with the blood or bodily fluids of an infected person.
The Ebola epidemic has spread through Liberia, Guinea and Sierra Leone, while Nigeria has also been affected. It is the worst outbreak of the killer virus yet.
The World Health Organization has warned it could take several months to bring the epidemic under control.