A buoy recorded the wave on Tuesday during a ferocious storm in the notoriously wild Southern Ocean near Campbell Island, some 700 kilometres (430 miles) south of New Zealand, research body MetOcean Solutions said.
Senior oceanographer Tom Durrant said it wiped out the previous southern-hemisphere record of 22.03 metres recorded in 2012.
"To our knowledge it is largest wave ever recorded in the southern hemisphere," he said, adding that the Southern Ocean was an "engine room" for generating swell waves that move across the planet.
"Indeed, surfers in California can expect energy from this storm to arrive at their shores in about a week's time," he said.
Durrant added that even bigger waves topping 25 metres were probably whipped up by the storm, which tracked east through the area on Tuesday, but the buoy was not in the best place to record them.
"It's very probable that larger waves occurred while the buoy was not recording," he said.
The largest wave ever noted was an earthquake-generated tsunami at Alaska's Lituya Bay in 1958 that measured 30.5 metres, according to Smithsonian magazine.
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