According to Official Guinness Records,
The youngest radio presenter is Kimberley Perez (b. 20 February 1998) (USA) who hosts a show every Saturday 3-7pm, on KLAX 97.9 La Raza FM, in Los Angeles, California, USA, which started when she was 5 years old. Perez began radio presenting by accidentally broadcasting on the air, aged 4. The response was overwhelming and she is well known in Los Angles County Latino radio stations and appears at local concerts promoted by La Raza FM.
For a complete list of Unknown date records, please visit Unknown date Guinness Records in United States.