Greta Thunberg spoke as part of a panel at the UN Youth Climate Summit on Saturday, a day after mass climate protests that she inspired began across the world.
You can watch her speech in the video player, above.
Thunberg gave a brief statement alongside other climate activists, Bruno Rodriguez, Wanjuhi Njoroge and Komal Karishma Kumar. António Guterres, the U.N. Secretary General, also spoke on the panel.
Guterres credited young activists for their work in highlighting the challenge of climate change and urged them to continue their struggle.
Thousands turned out on Friday from New York to New Delhi, London to Johannesburg, for rallies that came more than a year since Thunberg skipped school to carry out a one-person protest outside the Swedish parliament in 2018.
Her actions inspired the global “Fridays for Future” weekly school walkouts, and a global focus on the impact of climate change - particularly on the youth.
Since she crossed the Atlantic in an eco-friendly boat, the 16-year-old has spoken before the US Congress, met Barack Obama, and held a sit-in on the steps fo the Supreme Court.
Speaking to Congress, Thunberg said: “This is not the time and place for dreams. This is the time to wake up.”
Obama described the teenager on Twitter as “already one of the planet’s greatest advocates".