The 26-year-old model has been confirmed as the new host and executive producer of the popular TV series, replacing the German beauty in the process.
It's also been announced that Christian Siriano will take over TIM GUNN's role as mentor, with Elle magazine editor-in-chief Nina Garcia returning as a judge alongside newcomers Brandon Maxwell, a designer, and former Teen Vogue editor-in-chief Elaine Welterorth.
Looking forward to her new role, Karlie explained: ''As someone who grew up watching 'Project Runway', I could not be more excited to host and produce a series that provides a platform to aspiring American designers as they pursue their creative and entrepreneurial dreams.
''I am equally as thrilled to work alongside an incredibly talented group of fashion innovators - Brandon Maxwell, Elaine Welteroth, Nina Garcia and Christian Siriano - to inspire, support and help guide these designers as they realise their visions and build everlasting brands and businesses.''
Heidi, 45, announced her exit from the show in September, with the world-famous model revealing that she and Tim are set to star on a new fashion reality show with Amazon.
She said in a statement: ''After 16 incredible seasons, I am saying 'Auf Wiedersehen' to 'Project Runway', a show that I was honoured to host and help create.
''I am incredibly proud of the show, and it will always have a special place in my heart. I am so appreciative of the dedicated fans, and most of all, I am grateful that we could shine a light on creativity and help launch so many talented designers' careers.
''I'm most excited that my journey with my dear friend and colleague, Tim Gunn, is far from over. We will be partnering with Amazon for a new show, and we're excited for everyone to see what we're designing next!''
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