The British artists will hit the stage in Hamburg on 6 July (17), on the eve of the 2017 G20 Summit, where world leaders will be gathering to discuss Global Goals for Sustainable Development.
Those attending the gig will use the show to call on top politicians to address issues of education, health, development, and the refugee crisis at the G20 Summit.
"It is truly inspiring to see so many people come together and take action, participating in these essential conversations, and holding world leaders to account," Ellie says in a statement. "After joining the Global Citizen Festival on stage in New York last summer I am incredibly excited to continue on the journey to a sustainable future free of extreme poverty by performing in Hamburg on July 6."
As with other Global Citizen events, tickets will be free to fans who sign up to become a part of the charity and agree to offer support to "education, equality, and sanitation campaigns" in their community and beyond.
The Global Citizen Festival launched in 2012 and takes place annually in New York City's Central Park.
Last year (16), Coldplay and Jay Z performed at the first ever Global Citizen Festival in India.