At a meeting in Australia, it was agreed that around 1.5 million sq km of a part of the Southern Ocean would be protected from companies wanting to fish there for the next 35 years.
The Ross Sea actually only makes up about 2% of this ocean, but it is home to a huge amount of wildlife.
Environmental campaigners have welcomed the decision saying it will help to protect Earth's cleanest area of ocean.
They hope it will be the first of many such zones across the world.
You will find around two in every five of the world's Adelie penguins here, around one in three Antarctic petrels and around one in 16 of the world's minke whales. Killer whales live there too.
It is also a rich source of krill, which is food for seals and whales, so it's very important that it is looked after.
Here are 10 things you probably didn't know about Antarctica...
Antarctica isn't a country - it's a whole continent!
It is sits at the Earth's south pole and is almost completely covered by an massive ice sheet that is thousands of metres thick.
Antarctica is absolutely enormous. It is almost 14 million sq km, which makes it the fifth-largest continent behind Asia, North America, South America and Africa.
This is about 58 times the size of the UK and twice the size of Australia!
It is also the world's highest continent, with an average land height of 2,300 m.
The temperature on Antarctica has been known to go as low as around âˆ’90Â°C.
Because it is so cold, the air cannot hold as much moisture so it does not rain very much at all there.
This actually means Antarctica is considered to be a desert, but the other deserts that you know are much warmer...!
The winds can always blow as strongly as up to 351 km per hour.
As it is such an important place for scientific research, at any one time there may be many hundreds scientists spread across the various research stations all over the continent.
You will also find tourists there. According to Discovering Antarctica, in the early 1990s, about 5,000 tourists went every year. By 2009-2010, the continent welcomed around 37,000 visitors.
But nobody lives there permanently!
In the winter, the sea around Antarctica freezes over creating what is called sea ice. This makes the continent almost twice as big in winter.
The end of the summer in Antarctica is in March and the end of the winter is in September - opposite to in the UK!
This is because Antarctica is in the Southern Hemisphere, which faces the Sun during our winter time.
In 1959, several countries signed an agreement called the Antarctic Treaty, saying that Antarctica would be a peaceful place that they would work together to look after.
Without an international agreement like this, people would be free to do what they wanted there. However, this meant countries now work together to protect it.

Bilel Ayadi, 34, who is in a medically-induced coma, has been unable to tell detectives how he sustained burns to his torso and neck.
He was found walking in Finsbury Park, north London, on 23 March.
Mr Ayadi had walked bare-chested for about two miles, police said.
He was found in Woodberry Grove at about 22:30 GMT by two security guards, who called police.
Appealing for information, Det Con Anwen Clissold said Mr Ayadi would have "been very distinctive".
"It may well be that he was already injured as he made his way through the streets," she said.
"We are still trying to establish what has caused his burns but what we do know is that a young man has sustained some very serious injuries. I need to find out how."
Mr Ayadi's brother, Abderrezak Ayadi, said: "Bilel is my brother and at this moment he is lying in hospital with terrible injuries.
"Imagine if this was someone from your family. We just need to find out exactly what happened to him."
Algerian national Mr Ayadi, who has lived in the UK for the past six years, is described as 5ft 11in (1.8m) tall and of medium build.
Officials from 24 countries and the European Union have agreed that the Ross Sea, in Antarctica, will become the world's largest marine protected area.
[NEXT_CONCEPT]
Images of a shirtless man found wandering the streets after he suffered serious burns have been released in a bid to solve the mystery of his injuries.