The Irish presenter, 30, has hosted the popular I'm A Celebrity spinoff show on ITV2 since 2011 but announced overnight she's leaving the series to focus on other projects.
In a statement, she said: "After five incredible series working with my extended I'm A Celeb family, I've taken the tough decision to hang up my jungle boots. It's been such a wonderful experience but I feel it's time to move on. I wish the team well and look forward to tuning in later this year as well as continuing to work with ITV on other shows."
She added on Instagram: "Five incredible series! Sorry to say goodbye but been thinking about it for a long time and it's time. Still my favourite show on the telly!!"
A replacement has yet to be announced by ITV.
I'm A Celebrity... Get Me Out Of Here NOW!, which films yearly in Australia, was previously hosted by Caroline Flack. It airs directly after the main jungle show, fronted by Ant & Dec, and features behind the scenes gossip from camp, celebrity guests and previews of upcoming trials and challenges.
It's also been announced that comedian David Morgan will not be returning to Get Me Out Of Here NOW! after one series.
A rep for the show said: "We're sad to see them go and wish them all the best."
I'm A Celebrity and NOW! return to ITV later this year for its 16th series. Last year's show was won by former Geordie Shore star Vicky Pattison.