Meath native Reilly will succeed Ursula Halligan who spent close to two decades in the position.
New 10 year contracts have been given to Communicorp stations Today FM and SPIN South West and two community stations.
Scroll down to see the new brand campaign for the national station.
Tesco has been announced as the new sponsor of Dermot and Dave’s mid-morning show on Communicorp's Today FM.
The lads are kicking off the Ah Sure Lookit in Killarney tonight.
Communicorp's Today FM has a new website, new app and a refreshed logo now in use.
News of his appointment was broadcast live on-air and on Facebook live just after 11am Wednesday, during Dermot & Dave's new morning show.
Ann joined Today FM 13 years ago in 2004 after two weeks on work experience. Since then she hosted spots on, and been part of, Tom Dunne's show, Ray Foley's Show and the Ray D'Arcy Show.
The voice of Manchester United joined Today FM after three decades commentating on the football club for Piccadilly Radio in England.
Today FM lunchtime duo Dermot & Dave are to host a brand new mid-morning show on the national station, replacing Anton Savage.