"We now have a name for the disease and it's Covid-19," WHO chief Tedros Adhanom Ghebreyesus told reporters in Geneva.
The new name is taken from the words "corona", "virus" and "disease", with 2019 representing the year that it emerged (the outbreak was reported to the WHO on 31 December).
It comes after the death toll from the virus passed 1,000. Tens of thousands of people have been infected.
Dr Ghebreyesus called on the world to fight the new virus as aggressively as possible.
The word coronavirus refers to the group of viruses it belongs to, rather than the latest strain.
The virus itself has been designated SARS-CoV-2 by the International Committee on Taxonomy of Viruses.
Researchers have been calling for an official name to avoid confusion and stigmatisation of any group or country.