The patient died from the acute viral illness at a hospital run by the Bedfordshire Hospitals NHS Foundation Trust.
The UK Health Security Agency (UKHSA) said the person died from a confirmed case of the animal-borne disease, which is endemic in parts of West Africa.
The death comes as the third case of Lassa fever was identified in the UK in the last few days.
It said the risk to the public was "very low", as most people will make a full recovery but the illness can be fatal.
Lassa fever, like Ebola, the disease is endemic in a number of West African countries and can be spread through contact with the bodily fluids (blood, saliva, urine or semen) of infected people.
Humans can also get it by coming into contact with the urine or faeces of infected rodents that carry the disease.
The disease typically causes a fever and flu-like symptoms, but it can cause bleeding through the nose, mouth and other parts of the body.
The cases are the first of the disease to be confirmed in the UK in more than a decade.