Comte Jules Raphaël Bethenod de Montbressieux

Born the heir to a leading French noble family, de Dion in 1901 succeeded his father Louis Albert William Joseph de Dion de Wandonne as Count and later Marquis. He was described as a notorious duellist but possessed a strong passion for mechanics. In 1881 he encountered a model steam engine in a shop window and sought out the engineers behind it: Georges Bouton and his brother-in-law Charles Trepardoux, who operated a workshop producing scientific toys and shared Trepardoux's long-held dream of building a steam car.

The three formed a partnership in 1883 that became the De Dion-Bouton automobile company, eventually the world's largest automobile manufacturer for a period. Early experiments with marine steam engines gave way to a steam car that used belts to drive the front wheels while steering with the rear; this prototype was destroyed by fire during trials. In 1884 they built a second vehicle, known as La Marquise, with steerable front wheels and drive to the rear wheels. As of 2011 it was recognised as the world's oldest running car, capable of carrying four people at up to 38 miles per hour.

The de Dion tube — the dead-axle arrangement that separates the differential from the driven wheel hubs — was in fact invented by Trepardoux, who resigned from the company shortly before its introduction because the firm was transitioning from steam to internal combustion. In 1898 de Dion co-founded the Salon de l'Automobile, the Paris Motor Show.

Motor racing in France arose directly from public enthusiasm for the new automobile technology, with manufacturers seeing competition as an opportunity to demonstrate their vehicles. The first motor race took place on 22 July 1894, organised by the Parisian newspaper Le Petit Journal over the 122-kilometre distance between Paris and Rouen. De Dion's steam-powered car crossed the finish line first, but he was not awarded the first-place prize because his vehicle required a stoker — an assistant to manage the steam boiler — which the judges ruled was outside the competition requirements.

An earlier event in 1887, organised by cycling magazine Le Velocipede Illustre, is sometimes cited as Europe's first motoring competition. De Dion entered and was the sole participant, completing the course without opposition.

De Dion was a passionate anti-Dreyfusard whose political activities had lasting consequences for French sport. At an 1899 horse-race meeting at Auteuil, amid demonstrations over the Dreyfus affair, de Dion struck French President Emile Loubet on the head with a walking stick; he was jailed for 15 days and fined 100 French francs. The pro-Dreyfus editor of Le Velo, Pierre Giffard, heavily criticised de Dion's behaviour.

In response, de Dion withdrew his advertising from Le Velo and in 1900 led a coalition of wealthy anti-Dreyfusard manufacturers — including Edouard Michelin and Adolphe Clement — to found a rival daily sports paper, L'Auto-Velo, in direct competition with Le Velo. A further motivation was that Le Velo was financially backed by the Darracq company, a commercial rival of de Dion and Michelin, and the paper was felt to favour Darracq's products. After a legally enforced name change to L'Auto, the paper created the Tour de France cycle race in 1903 to boost its falling circulation. L'Auto later became L'Equipe, the major French sports newspaper.

De Dion was an active writer who contributed columns to Le Figaro, Le Matin, and other publications. His wealth also allowed him to revive Le Nain Jaune, a fortnightly publication. He died in 1946 at the age of 90 and is buried in Montparnasse Cemetery in Paris.

De Dion's contributions span the founding era of both the automobile and organised motor competition. De Dion-Bouton's engineering output, the first recorded road race victory, the establishment of the Paris Motor Show, and the indirect creation of the Tour de France and L'Equipe together represent an outsized influence on modern motorsport and sporting media.