Cyril Posthumus (28 August 1918 – October 1992) was a British writer on the history of motor cars.
His works include:
- The British Competition Car
- Land Speed Record: A Complete History of the Record-Breaking Cars from 39 to 600+ m.p.h.
- Sir Henry Segrave, a biography of the British racing car driver. Publ. 1961 BT Batsford Lts, London
- The 1926–1927 1½ Litre Delage, on the car made by the French firm Delage
- Vintage Cars, concerning cars made in the 1920s.
- numerous articles in Road & Track, Car and Driver, etc.