The announcement, made in a statement and at a meeting of the Global Polio Eradication Initiative in New York, leaves just two countries — Pakistan and Afghanistan — on the list.
In declaring Nigeria “no longer polio endemic”, the WHO said: “This is the first time that Nigeria has interrupted transmission of wild (naturally occurring) poliovirus, bringing the country and the African region closer than ever to being certified polio-free.”
The last case was in the Sumaila district of Kano state, northern Nigeria, on July 24, 2014.
Countries have to go at least 12 months without a case before they can be considered for removal from the list while polio-free status comes after three years without a case.
The WHO said “all laboratory data have confirmed a full 12 months have passed without any new cases”.
The announcement is the latest good news in the global battle against the virus, which is spread by poor sanitation and contaminated water and can cause irreversible paralysis.
Children under-five are particularly vulnerable.
On August 12, Africa marked one year since the last recorded case of polio — in Somalia — raising hopes of its elimination across the continent.
But there is still concern about vaccination gaps, particularly in hard-to-reach areas, that could hinder the complete eradication of the disease.
In 2015, 41 cases of wild poliovirus have been reported worldwide — 32 in Pakistan and nine in Afghanistan.