Denis Hegarty (born 13 September 1954) is an Irish rock and roll, doo-wop and a cappella singer, television presenter, and psychology lecturer.

As the former BBC radio executive Lesley Douglas later recalled of a 1970s gig: "I remember sitting in the front row terrified of the Darts singer Den Hegarty, because all the papers had said that he was the mad man of music and that he would dive into the crowd".

[7] Music journalist Will Hodgkinson recounted another incident, during a Spanish eurovision TV show in 1979, where "the grandiosity of the whole affair proved too much for the bug-eyed Hegarty, who felt compelled to jump into a fountain and roll around in it, mid-performance", before taking off his socks and wringing them down the neck of actress Sylvia Kristel.

[8] Dave Haslam recalled how Hegarty "had a thing for clambering on the speaker stacks at the side of the stage (by far the highlight of the set)".

[6] After the demise of Tiswas, Hegarty became a cable show quizmaster, and then took another direction providing voices for animated characters in television advertisements.