What was Wilma's maiden name on The Flintstones?

Wilma Flintstone's maiden name was Pebble.

This fact was established early in the original The Flintstones animated series, where her pre-marital surname was consistently referred to as Pebble in several episodes.

For instance, in the second-season episode titled "The Entertainer," an old friend of Wilma's, Greta Gravel, clearly remembers and refers to her as "Wilma Pebble." Similarly, in the third-season episode "Dial S for Suspicion," an old boyfriend of Wilma's also addresses her by her maiden name, "Wilma Pebble," reinforcing this detail within the show's continuity.

Below is a quick reference for Wilma's maiden name:

For more details on Wilma Flintstone and other characters from the series, you can explore her Wikipedia page.