Usually mild, it is fatal in rare cases.
It causes flu-like symptoms and pus-filled lesions on the body.
"This decision is based on sustained declines in cases and as in the Democratic Republic of Congo and in other affected countries including Burundi, Sierra Leone and Uganda," Tedros Adhanom Ghebreyesus said.
Children, pregnant women and people with weakened immune systems, such as those with HIV, are all at higher risk of complications.
The WHO said Mpox was still a public health concern across the world but it had decided to downgrade it based on advice from its Emergency Committee, which meets every three months to evaluate the outbreak.
"While we are removing the emergency, we need to keep the urgency," Professor Dimie Ogoina from the Emergency Committee said.
"This is not a time for us to reduce the investments in terms of financial investment, partnership, solidarity, especially for most affected countries in the African continent," he added.
Out of the recorded cases, there had been worrying levels of deaths among people living with HIV AIDS, particularly in Uganda and Sierra Leone, and signs of vulnerability among infants and children in DR Congo, Ogoina said.
The new form of Mpox, clade Ib, continues to predominantly impact sub-Saharan Africa.
There have also been travel-related cases in Thailand, the United Kingdom and other countries.
The WHO first declared the emergency in August last year, when an outbreak of a new form of mpox spread from the badly-hit DR Congo to neighbouring countries.
Mpox was formerly known as monkeypox.
A public health emergency of international concern is WHO's highest form of alert.
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