From Longman Dictionary of Contemporary Englishfolk heroˈfolk ˌhero noun [countable] RFsomeone who people in a particular place admire very much because of something they have done Casey Jones is an American folk hero.
Examples from the Corpus
folk hero• Ferguson is flawless, a folk hero in two countries.• The affair seemed only to add to his status as folk hero.• He was a celebrated folk hero in his adopted Darlington from his arrival in 1919 to his death in 1946.• Just the kind of marginal folk hero they would go and use as a mascot. 