Ernest Arthur Douglas Eldridge (18 July 1897 – 27 October 1935) was a British racing driver who broke the world land speed record in 1924. His was the last land speed record set on an open road.

Eldridge was born on 18 July 1897 at Willesden in Middlesex to a wealthy family. His father was a successful bill discounter. Educated at Harrow School he quit while in the 6th form to go to the Western Front, in the First World War. Eldridge joined the British Red Cross Society and Order of St John of Jerusalem, possibly as an ambulance driver. He may have also served in the French Artillery.

Eldridge married Majorie M. Tooth in 1915 at Brentford in Middlesex; she died before the Second World War. A bigamist, he married a second time in 1925 to a French woman named Marie, whom he eloped with while still married to Marjorie.

Not much is known about the years between 1918 and 1921 when Eldridge reappeared at Brooklands. There are unconfirmed myths about him flying with Louis Zborowski. He was a pilot, surviving a crash in a B.E.2e at Brooklands in September 1922. He learned to fly in a Sopwith Grasshopper at Brooklands and finally received his pilot's licence (Number 7944) on 21 August 1923 at Stag Lane Aerodrome, Edgware. His licence lists his profession as Automobile Engineer.

The early part of Eldridge's racing career is littered with failures of large, often aero engined, racing cars. His first racing appearance was in 1921 with a rare chain-driven Isotta Fraschini which was lapping at more than 90 mph.

In 1922, Eldridge startled the Brooklands crowd by appearing with a 240 horsepower (180 kW) Maybach aero engine in his 1907 Isotta Fraschini chassis, which had been stretched to accommodate the giant power plant. This 20-litre racer had a tiny two-seater body made by Jarvis of Wimbledon and caused something of a sensation, even when monstrosities were not uncommon in motor racing circles. It won its first race at more than 101 mph (163 km/h) but over all was not terribly successful. He sold it to another British racing driver, L C G M Le Champion.

Eldridge then turned to a 10-litre Fiat, which he drove with some success. With the proceeds he bought Mephistopheles, and embarked on his famous escapades. In October 1923 at Brooklands: "E. A. D. Eldridge set up new figures for the half-mile (standing start) world's record by covering the distance in 23.17secs. (77.68 miles an hour) on his giant 350 horse-power F.I.A.T." and taking the World Land Speed Record on 12 July 1924 at Arpajon, France, at an average of 146,013 mph (234,985 km/h) over the flying kilometre. In October 1924, at Montlhéry: "Mr. Eldridge covered 210 kilometres 230 metres in the hour, and at one time attained 218 kilometres (over 136 miles) an hour. This is claimed to be a world's record."

In 1925, Eldridge sold Mephistopheles to Le Champion and decided to enter the world of Grand Prix motor racing with cars of his own design, the Eldridge Specials. Based on Amilcar chassis with Anzani engines, these cars were entered at many races for the 1925 and 1926 seasons including the Brooklands 200, The San Sebastian, the L'ACF and the Italian GPs. He also entered two cars in the 1926 Indy 500, no doubt tempted by the prize money. He drove one car with Douglas Hawkes in the other.