The famous neon lights will be switched off at 20:30 GMT as United's stadium joins other world landmarks such as the Empire State Building in New York, Paris’s Eiffel Tower and the Sydney Opera House in demonstrating a commitment to tackling climate change.
United have taken part in Earth Hour for the last three years as part of the club’s wider ‘Reds Go Green’ environmental programme.
This year, WWF is calling on the club's fans to show their support and join the hundreds of millions of people across the world who will be taking part in Earth Hour. To get involved, visit www.wwf.org.uk/earthhour.
Reds legend Gary Neville has already signed up and will be switching off his lights at 20:30 GMT on Saturday for an hour. He's asking supporters to do the same.
"We can all do more to help us live within the natural resources we have. Switching off for WWF's Earth Hour is a great way of reaching more people and changing more minds."
– Gary Neville
To find out more about Earth Hour and to join in, visit www.wwf.org.uk/earthhour.