Video report by ITV News Science Correspondent Alok Jha
Delegates from 24 countries and the EU have agreed to create the world's biggest marine reserve area in Antarctica.
The area, which is more than six times the size of the UK, will protect 1.55 million square kilometeres (600,000 square miles) of the Ross Sea, and has been hailed as a "milestone for conservation".
The agreement was reached by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), and the protected area will come into force in December 2017.
Almost three-quarters (72%) of the conservation area, which forms part of one of the last intact marine ecosystems in the world, will be a "no-take" zone, where all fishing is forbidden.
This will protect wildlife such as Adelie and Emperor penguins in remote parts of the Antarctic sea.
Other areas of the protected area will allow some fish and krill to be harvested for scientific research.
The deal was put together by New Zealand and the US, and became a reality after Russia agreed to the move after holding initially holding out.
John Hocevar, a marine biologist with Greenpeace, said: "This is a victory for the whales, toothfish and penguins that live in the Ross Sea, as well as for the millions of people who supported this effort.
"We urge the international community to take notice and designate additional, permanent protections in other areas of the Antarctic Ocean and around the world."
The agreement to establish the protected area comes after conservationists warned of a mass extinction of global wildlife populations on a scale not seen since the disappearance of dinosaurs.
Experts said populations of species such as the African elephant and the killer whale are predicted to fall by more than two-thirds on 1970 levels by the end of the decade.