Earth Hour is a worldwide movement organized by the World Wide Fund for Nature (WWF). The event is held annually encouraging individuals, communities, and businesses to turn off non-essential electric lights for one hour, from 8:30 to 9:30 pm on a specific day towards the end of March, as a symbol of commitment to the planet. It was started as a lights-off event in Sydney, Australia, in 2007. Since then, it has grown to engage more than 7,000 cities and towns across 187 countries and territories to raise awareness for energy consumption and effects on the environment.

Occasionally, in years when Holy Saturday falls on the last Saturday of March, Earth Hour is moved a week early rather than its traditional date.

Earth Hour 2018 was on March 24, from 8:30 pm to 9:30 pm.

Earth Hour 2019 is scheduled for March 30, from 8:30 pm to 9:30 pm