Delegates from 24 countries and the European Union have agreed that the Ross Sea in Antarctica will become the world's largest marine protected area (MPA), BBC reports.
Some 1.57m sq km (600,000 sq miles) of the Southern Ocean will gain protection from commercial fishing for 35 years.
Environmentalists have welcomed the move to protect what's said to be the Earth's most pristine marine ecosystem.
They hope it will be the first of many such zones in international waters.
At this meeting in Hobart, Australia, the Commission for the Conservation of Antarctic Marine Living
Resources (CCAMLR) agreed unanimously to designate the Ross Sea as an MPA, after years of protracted negotiations, New Zealand Foreign Minister Murray McCully announced.
The Ross Sea, its shelf and slope only comprise 2% of the Southern Ocean but they are home to 38% of the world's Adelie penguins, 30% of the world's Antarctic petrels and around 6% of the world's population of Antarctic minke whales.
The region is important to the rest of the planet as the upwelling of nutrients from the deep waters are carried on currents around the world.