The WHO said the decision was made due to the 'alarming levels of spread and severity'.
A pandemic is classed as the 'worldwide spread of a new disease', according to the WHO.
Director General of the WHO Tedros Adhanom Ghebreyesus said the decision hadn't been taken lightly, though it doesn't affect its advice to countries.
He said: "Pandemic is not a word to use lightly or carelessly. It is a word that, if misused, can cause unreasonable fear, or unjustified acceptance that the fight is over, leading to unnecessary suffering and death.
"Describing the situation as a pandemic does not change WHO's assessment of the threat posed by this coronavirus. It doesn't change what WHO is doing, and it doesn't change what countries should do.
"We have never before seen a pandemic sparked by a coronavirus.
And we have never before seen a pandemic that can be controlled at the same time.
WHO has been in full response mode since we were notified of the first cases.
"We have called every day for countries to take urgent and aggressive action. We have rung the alarm bell loud and clear."
He went on to say that 81 countries have so far reported no cases of Covid-19, while 57 countries have reported 10 cases or less, adding that even in countries where the virus is widespread it can still be suppressed.
As of 9am today, 456 people in the UK have tested positive for the virus and six people have died.
It's okay to not panic. LADbible and UNILAD's aim with our campaign, Cutting Through, is to provide our community with facts and stories from the people who are either qualified to comment or have experienced first-hand the situation we're facing. For more information from the World Health Organisation on Coronavirus, click here.