The Riley 1 1/2 is a mid-size vehicle that Riley introduced in 1936 as a successor of the 12/4.

All versions had an 4-cylinder inline engine with 1,496 cc displacement and an output of 51 bhp (38 kW), like its predecessor, the engine was fitted with 2 Zenith carburettors. Chassis and bodies were consistent with the Riley 15/6. The two models on the short chassis (wheelbase of 2,769 mm), Falcon (4-window sedan) and Lynx (Tourer), reached 107 km/h. The two large hatchback sedans (6 windows, wheelbase of 2857.5 mm) Adelphi and Kestrel, reached 117 km/h. There was also the Merlin, a roadster on a shortened chassis (wheelbase of 2692.5 mm), which reached a top speed of 113 km/h.

In 1940, the production was stopped due to the war. Successors were the RM models which appeared in 1946.