Daffy Duck was voiced by Mel Blanc from 1937 until 1989, making him one of Blanc's longest-running character roles.

Britannica confirms that from Daffy's first appearance through 1989, the character was performed by famed voice actor Mel Blanc. The Simple Wikipedia entry lists Mel Blanc as the voice actor from 1937 to 1989, followed by a succession of other voice actors including Jeff Bergman, Joe Alaskey, Greg Burson, and more recently Eric Bauza from 2018 onward. Mel Blanc's tenure of over fifty years with a single character is remarkable even by his standards, which included Bugs Bunny, Tweety, and Porky Pig.