It's part of Earth Hour, an event that encourages participation in fighting climate change. This year the event is celebrating its 10th anniversary.
The World Wildlife Fund says Earth Hour is not a one-hour commitment to conservation but rather a symbol of something bigger.
"Participation in Earth Hour symbolizes a commitment to change beyond the hour," the website reads.
The initiative is supported by 7,000 cities around the world. Landmarks will go dark, and millions of people are expected to turn off their lights.
Earth Hour takes place at 8:30 p.m. - 9:30 p.m. local time.