The Alvis Speed 20 was a British touring car made between late 1931 and 1936 by Alvis Car and Engineering Company in Coventry. It went through four variants coded SA to SD.In October 1935 the Speed 20 was supplemented by a 3½-litre car initially sold alongside their Speed 20 SD and named 3½-litre SA. After their Speed 20 was dropped from their catalogue the 3½-litre car was given a shorter wheelbase and named Speed 25 SB.