They are also dismissive of myths that he owned a horse called Black Bess - the trusty steed is supposed to have helped him escape from many a chase with police.
This revision of folk mythology has been made by historians at the York Castle Museum, formerly the prison where Turpin was held to await death.
They have also rubbished suggestions that he made his legendary ride from London to York.
Michelle Petyt, assistant curator of social history at the museum, said research suggested he was a "quiet and dour man" and that stories of his good looks were definitely untrue.
Professor James Sharpe, criminal history lecturer at York University - who is preparing a book about Turpin - said Turpin's crimes were equally unappealing.
He said: "Any ideas that he is a romantic, dashing figure are a nonsense. He had a quick temper and a violent streak."
There was a huge public appetite in previous centuries for stories about Dick Turpin, but he was never sketched before his execution in April 1739 for the capital offence of horse stealing.
Engravings highlighting his handsome features only emerged years later and they bear no likeness to how he actually looked.
The most reliable testimony about him comes from John Wheeler, a one-time Turpin gang member turned police informer.
In 1735 he described the highwayman as a "tall, fresh-coloured man, very much marked with the pox," who wore a light wig.
A later description in the Police Gazette described him as: "Cheekbones broad, his face thinner towards the bottom, his visage short, pretty upright and broad of the shoulders."
Even his winning ways with the ladies have proved to be exaggerated.
The traditional notion of Turpin has him kissing maidens before escaping through the windows of coaching inns, but Professor Sharpe attributes this to the end of 19th century romantic novelist Harrison Ainsworth.
Ainsworth, whose popularity rivalled that of Charles Dickers in Victorian times, wrote a melodrama called Rockwood, in 1834, which detailed the handsome Turpin's exploits on Black Bess.
That version of Turpin's life coincided with the arrival of the railways - when highway robbery ceased to be a major crime in England.
"It's an example of crime becoming romanticised at a time when it stops being dangerous", said Professor Sharpe.