Former Blue Peter presenter Katy Hill will be one of the new presenters of commercial radio's Hit 40 UK chart show following Neil Fox's decision to quit.
Katy Hill will take over the reins with Hirst in June
The DJ, who announced he was leaving at the end of last year, will count down his last Sunday show on 30 May.
Hill and co-host Simon Hirst will take over the chart show, broadcast by 113 radio stations, on June 6.
Hirst, 28, hosts the breakfast show on Yorkshire station Galaxy 105, while Katy Hill left Blue Peter in 2000.
Fox, who has been at the helm of the show for 11 years, said: "I've seen out Take That, the Spice Girls, Britpop, the explosion of dance music and now the massive success of R&B.
"That's almost a whole generation of pop music right there.
"Now is definitely the right time for me to move on and I'm handing over to a great team."
Hill said there would be some "exciting new ideas" but "all the good stuff will still be in there".
Hirst said: "Katy and I met for the first time at a demo in the Hit 40 studio and the on-air chemistry was immediately there.
"I'm sure we'll have lots of fun. They're big headphones to fill but we're really excited about the challenge."
Hill and Hirst will compete with BBC Radio 1's Official UK Chart Show with Wes Butters, and a rival commercial radio countdown, the Smash Hits Chart with Mark Goodier.