Dylan is usually credited with inventing "folk rock" but he himself said "I don't play folk rock".

Nobody really invented "folk rock", certainly not Steeleye Span or any of those bands, though they certainly brought it into the mainstream with hit singles, etc. "Folk rock" just kind of evolved gradually: I mean, Enoch Kent was singing traditional songs backed by electric guitar and drums back in '63, way before the Byrds, etc.

The real question is how should "folk" music be defined: and that ain't possible!