The 38-year-old royal will be joining a virtual panel consisting of impassioned climate activists such as Al Gore, Jaden Smith, Chris Hemsworth, Mark Ruffalo, Yemi Alade, and Don Cheadle, where they will discuss how the world can tackle climate change and ensure a healthier future for the planet.
The event, which has been named Countdown, will also be the first-ever free TED Talks conference, and will take place on Oct 10.
Alongside the celebrity appearances, the event will bring together "scientists, activists, entrepreneurs, urban planners, farmers, CEOs, investors, artists, government officials," and more to "find the most effective, evidence-based ideas" to help combat climate change.
While the conference will mark the first time William has spoken at a TED Talk, the royal has been vocal about climate change in the past, as he said last year the Earth is "at a tipping point".
He said in December: "The earth is at a tipping point and we face a stark choice: either we continue as we are and irreparably damage our planet or we remember our unique power as human beings and our continual ability to lead, innovate and problem-solve.
"People can achieve great things. The next ten years present us with one of our greatest tests - a decade of action to repair the Earth."
Meanwhile, Chris Anderson, the Countdown founding partner and Head of TED, said he hopes to "unite all levels of society" with the upcoming conference.
In a statement, he said: "The moment to act on climate change has been upon us for too long, and now is the time to unite all levels of society - business leaders, courageous political actors, scientists and individuals - to get to net-zero emissions before 2050.
"Climate is a top priority for TED and members of our community, and we are proud to fully dedicate our organisation in the fight for our collective future."