- Coronavirus pandemic
image source, Getty Imagesimage captionKylie Minogue is one of many stars to have pre-recorded a performance
Stars including Billie Eilish and Ed Sheeran are set to perform at a 24-hour concert to raise awareness of climate change, vaccine inequality and famine.
The Global Citizen festival will see performances from more than 60 artists in New York, London, Sydney and beyond.
Tens of thousands of people are expected to attend, while millions are likely to tune in to the broadcast.
The event kicked off on Saturday in Paris, where Elton John performed in front of the Eiffel Tower.
He took to the stage following a pre-recorded performance by the K-pop band BTS.
The show, believed to be one of the biggest-ever international charity events, was organised by the non-governmental organisation (NGO) Global Citizen.
"Across six continents, artists will help rally citizens in demanding that governments, major corporations and philanthropists work together to defend the planet and defeat poverty," it said in a statement.
It called on international governments to plant one billion trees, deliver one billion vaccines to the poorest countries and donate meals for 41 million people on the brink of famine.
In New York's Central Park, Billie Eilish, Jennifer Lopez and Coldplay will be joined on stage by the Duke and Duchess of Sussex, Prince Harry and his wife Meghan Markle.
Stevie Wonder will play in Los Angeles, while Ed Sheeran will perform in Paris alongside the Black Eyed Peas and Stormzy.
image source, Getty Imagesimage captionJennifer Lopez is among those set to perform in New York
There will also be pre-recorded performances from a huge number of stars, including Green Day, Kylie Minogue and Andrea Bocelli.
The Global Citizen organisation has been behind other high-profile charity events, including Vax Live: The Concert To Reunite The World earlier this year in Los Angeles.
That event brought together musicians, actors, celebrities, world leaders in a united call for global vaccinations to fight Covid-19.
The head of the World Health Organisation has backed Saturday's campaign, calling on the leaders of the developed world to unite and bring an end to vaccine inequality.
"We now face a two-track pandemic of haves and have-nots," Dr Tedros Adhanom Ghebreyesus said. "We cannot disregard this gross inequity or become complacent."
Those attending the concerts are required to produce either proof of vaccination or a negative Covid test.
Tickets to the shows were distributed free of charge to randomly selected people who signed up for the Global Citizen app and shared its petitions on social media.
Unlike most events of this nature, organisers are not aiming to raise cash but rather to use participation as evidence for world leaders that people support bold action on the issues.
The Global Citizen: Live concert is being shown on BBC One and iPlayer for audiences in the UK