The star, who has hosted the show since 2009, announced her intention to step down in a statement to fans.
She said it was “difficult” for her to say goodbye but thanked her “loyal and supportive viewers”.
ITV wants to hire two “heavyweight” presenters to replace Holly Willoughby on This Morning
However, ITV bosses reportedly want to replace Holly Willoughby on This Morning with two “heavyweight” presenters.
According to a show insider, Good Morning Britain’s Ben Shephard and Kate Garraway are apparently the frontrunners for the flagship show.
The source told Mail Online: “Ben and Kate will be adored by audiences when they host together. Fans love them.”
“While bosses love Alison Hammond and Josie Gibson, they know they need someone stronger. Kate is a journalist, but also funny and warm.”
Emma and Matt Willis, comedian Joel Dommett and his wife Hannah Cooper, as well as Peter Crouch and Abbey Clancy are also in the running for the presenting duties.
Beyond the presenters, it is reported that ITV is looking to do a complete overhaul of the show.
Another source said: “Holly’s decision to leave has sent shockwaves through the corridors of power at ITV, but there is now a feeling that change needs to be made – and this is the push needed.”
“This Morning boss Martin Frizell will continue to lead and work tirelessly to give viewers what they want – a warm, lively, feel-good magazine show hosted by two fresh new presenters.”