The US Geological Survey says the 5-point-8 magnitude quake struck just after 5 o'clock, local time.
It struck 172km east of Niuatoputapu at a depth of 10 kilometres.
There are no initial reports of damage and no tsunami warning has been issued.
Photo: US Geological Survey Caption: A map showing the epicentre of Wednesday morning's earthquake in the waters of Tonga's north.
Source:
RNZ Pacific