Fred Flintstone is one of the most iconic cartoon characters of all-time. Basically his voice was made famous by both Henry Corden and Alan Reed.
Some may not have realized this but for the pilot of the series, entitled "Flagstones" , voice acting legend Daws Butler provided the voice.
In the show, "Flintstone Kids", Lennie Weinrib provided the voice, however for certain parts, especially PSAs and a 'Just Say No' special, Scott Menville filled in.
Outside of a few parodies done by the likes of Maurice LeMarche and others Jeff Bergman has been the main person doing Fred's voice ever since the one-shot TV Special, "Flinstones on the Rocks" which aired in 2001 and was the last Flintstone project ever done by Hanna and Barbera.