Earth Hour is a global event organised by the World Wide Fund for Nature (WWF). Held every year, it encourages people and businesses to turn off their lights and other unnecessary electrical devices for one hour from 8:30 p.m. to 9:30 p.m. on the last Saturday of March. Earth Hour was started as a lights-out event in Sydney, Australia, in 2007. Since then, it has grown to become an international movement for the environment, happening in more than 7,000 cities and towns across 187 countries and territories.

Earth Hour has created a positive environmental impact. It shows the public support for protecting the environment and saving the planet. It also draws attention to climate change and global energy issues, and promotes green activities worldwide.

Viet Nam joined the event in 2009 and has been an active and keen supporter since then. Besides switching off lights, people can take part in a number of activities to raise awareness of environmental problems and call for action for climate, people and nature.