The only other to have done this was Indian Prime Minister Narendra Modi, who did this in 2014.
A substantial portion of O'Neill's address focused on climate change, which he described as the greatest challenge confronting Papua New Guinea and Fiji, and all Pacific Island Nations.
"Papua New Guinea, and our region, greatly appreciates Fiji's leadership on this issue. Fiji's central role at COP-23 in Bonn, Germany, is an example of the right approach we must take.
"While we in the Pacific did not cause climate change - our villages and towns, from our cities to our remote communities - are suffering from climate change. Extreme weather leading to cyclones such as Cyclones Josie and Keni this year, after Cyclone Winston in 2016, have been of terrible ferocity and severity.
"Extreme drought also crippled parts of Papua New Guinea in recent years. And we are seeing changes in our biodiversity - invasive species of pests and disease are on the move and destroying crops.
"Changes in ocean temperatures and water movements are destroying our fish stocks. Sadly, Papua New Guinea is the home to the world's first climate change refugees. The people of the Carteret Islands, in Bougainville, have seen their houses and their gardens washed away by tidal surges. They are now leaving behind the islands their people called home for thousands of years.
"This is not fair - it is simply not fair. Just as it is not fair that villagers in Fiji and every other island nation in the Pacific are being forced from their homes," he said.
O'Neill said the Pacific had to stand together, because if they did not stand up for themselves, no-one else would. He said Pacific countries, together with developing nations around the world from Africa to the Caribbean should work together in a combined effort to pressurise industrialised countries to reduce their emissions.
"We have to start to reverse climate change for the safety and health of our future generations. We are in this together - and as Pacific brothers and sisters, we will stand side-by-side and take on the rest of the world will take notice."
O'Neill said that PNG fully supported Fiji's leadership through the Talanoa dialogue which was being facilitated through the Climate Action Pacific Partnership.