Sarah, Duchess of York will present This Morning on Monday alongside presenters Alison Hammond and Dermot O'Leary.
Cat Deeley stepped in to co-present three shows last week as ITV looks to replace former presenter Holly Willoughby, who announced her departure from the program last month.
The 64-year-old duchess, known affectionately as Fergie, has enjoyed previous visits to the This Morning studio and is a guest editor as well as co-hosting the Monday show.
As part of her role as guest editor, Sarah will oversee the two-and-a-half-hour live program, starting at 10am, which will delve into issues close to her heart.
These include a look at the importance of defibrillators, the best way to rehabilitate a dog and how to protect your skin.
There will also be an interview with Sir Cliff Richard, who recently released the instrumental album Cliff With Strings – My Kinda Life, celebrating his 65 years in the music business.
Sarah will host some of these items alongside Hammond, 48, and O'Leary, 50.
The Duchess said: “I've appeared on This Morning before but this time I'm coming back in a very different role.
“I love live TV and I'm a huge fan of the show, and the whole team are always a pleasure to deal with.
“I'm looking forward to being there for the whole morning and I'm excited to be invited to curate the show, which will mean I'll be exploring some topics I'm passionate about.”
This Morning editor Martin Frizell added: “We are all delighted that Sarah, Duchess of York has wanted to come back here and I am delighted that she will be making some of my decisions on Monday.
“She really understands the show and how television works, and I think viewers are going to be really interested in the series she puts on with her.”
Sarah's one-day stint as co-presenter and editor of This Morning comes as presenter Josie Gibson enters I'm A Celebrity… Get Me Out Of Here! jungle.
The ITV series returns on Sunday evening with a line-up including former UK Independence Party (Ukip) leader Nigel Farage, food critic Grace Dent and Jamie Lynn Spears – sister of pop star Britney.
This Morning hit the headlines in May when Willoughby's former co-host Phillip Schofield quit the show after admitting to a “lewd but not illicit” affair with a younger male colleague.
ITV said it was “not given and found no evidence of a relationship beyond hearsay and hearsay” when it looked into the matter in 2020, and chief executive Dame Carolyn McCall said there would be an external review.
The daytime program has faced increased scrutiny as past and present workers have brought “allegations of toxic work cultures, bullying, discrimination and harassment” to MPs.
Dame Carolyn told the Culture, Media and Sport Committee in August: “We are absolutely committed to allowing people to raise any issues or complaints they may have about working at ITV.”
The broadcaster updated its industrial relations policy in October.