Apparently she wants to spend more time with her family. 'I love the job,' she says, 'But I've got other responsibilities – the children, a home life, and an elderly dad who needs me.'
Fiona started on GMTV back in 1993 when she was based in Hollywood, but was promoted to the sofa soon after.
We've picked out one of our favourite clips from her time at GMTV when she interviewed Heather Mills. Fiona manages to keep asking the tough questions while keeping a very angry Heather in check.
We'll miss her loads, but as long as Lorraine Kelly doesn't jump ship as well we reckon we'll be OK.