The Maserati 300S was a racing car produced between 1955 and 1958 for the FIA Sports Car Championship. In total, only 26 units were produced. It was produced as a 2-door convertible with rear-wheel drive and engine located in the front. It was powered by a 3-litre I6 engine based on the design of the Maserati 250F mated to a transverse 4-speed gearbox. It had a lattice construction and aluminium body.

After a poor showing in the first season, mainly due to mechanical failures, the 300S won the 1956 Nürburgring, finishing second overall. After the big crash at Guidizzolo, the last few examples of the 300S were sold to customers in the USA. One example of the 300S was developed with the new V12 engine and became the Maserati 350S.