The Riley Nine was one of the most successful light cars produced by the British motor industry in the inter war period. It was made by the Riley company of Coventry, England with a wide range of body styles between 1926 and 1938.

The car was largely designed by two of the Riley brothers, Percy and Stanley. Stanley was responsible for the chassis, suspension and body and the older Percy designed the engine.

The 1087 cc four cylinder engine had hemispherical combustion chambers with the valves inclined at 45 degrees in a crossflow head. To save the expense and complication of overhead camshafts, the valves were operated by two camshafts mounted high in the crankcase through short pushrods and rockers. The engine was mounted in the chassis by a rubber bushed bar that ran through the block with a further mount at the rear of the gearbox. Drive was to the rear wheels through a torque tube and spiral bevel live rear axle mounted on semi elliptic springs.

At launch in July 1926 two body style were available, a fabric bodied saloon called the Monaco at £285 and a four seat tourer for £235. The saloon could reach 60 mph and give 40 mpg.

The range was extended in 1929 with the Biarritz saloon which was a de-luxe version of the Monaco and a two seat tourer and improved brakes were fitted using the Riley continuous cable system that could be adjusted from the driver's seat.

More body variants were added over the next few years and in 1934 a Preselector gearbox was offered for £27 extra. The range was slimmed down in 1935 to the Monaco saloon, Kestrel streamlined saloon and Lynx four seat tourer.

A new chassis was introduced in 1936 and the brakes were changed to Girling rod operated and only the Kestrel and steel bodied Merlin saloons offered.

The final version was the 1938 Victor also available with 1496 cc engine and all steel body.

The Riley company was bought by Lord Nuffield in 1938 and after the war merged into BMC. The Nine engine carried on for a while and a version was last used in 1957 in the Pathfinder.