The Riley 2 1/2 was a vehicle of the upper middle class which Riley introduced in 1937.

The cars had a 4-cylinder inline engine with 2,443 cc displacement and an output of 82 bhp (60 kW). The engine was equipped with a SU carburettor and accelerated the roadster (with a 2946 mm wheelbase) up to 130 km/h.

In 1939, the production was stopped due to the war.

The successor was brought out in 1946 as the larger RM.