Annie Mac will cover Sara Cox's weekend programmes on BBC Radio 1 during her upcoming maternity leave.
Annie's first shows at the weekends will be 23 and 24 February and Sara will return to the station in September.
In other news, Nick Grimshaw joins Radio 1 to front Switch whilst Annie looks after weekends. Nick has been a weekly contributor to Switch since the show started in October 2007 and co-hosts the BBC Two music show Sound with Annie.
Annie will continue to host Annie Mac's Mash Up each Friday.
Annie Mac said: "I am delighted to look after Sara's show for her when she's having baby number two. I think Sara is an exceptional presenter, and I just hope I do her show justice for her when she's away. I know that Switch is in safe hands with my mate Grimmy looking after it. He's so funny on the radio and is properly passionate about new music. He'll do a super job."
Sara Cox said: "I'm really happy that Annie is going to keep my seat warm while I'm away, she's a good pal and I'm sure she'll be brilliant on the show."
Ben Cooper, head of programmes, Radio 1, said: "Everyone at Radio 1 wishes Sara all the best and we look forward to welcoming her back after her maternity leave. I'm very pleased that Annie is going to look after the show while Sara is away, she's a great broadcaster and I know she'll do a brilliant job. Nick has proven himself as part of the Radio 1 family and it's very exciting that he'll be hosting his own show during this period."