α-amylases are digestive enzymes which hydrolyze α-1,4-glycosidic bonds in starch. α-amylases have a lot of potential applications in food processing industries such as sugar, baking, brewing and preparation of digestive aids. Thermostable α-amylases have received a lot of importance because of their usage under harsh industrial conditions. α-amylases can be produced by microorganisms using submerged and solid state fermentation. However, solid state fermentation is attractive because of usage of cheap substrate, high yields and avoids substrate inhibition. This study reviews the microbial sources, fermentation characteristics and different substrates used for the production of thermostable α-amylases. In addition, the downstream processing of thermostable amylases and its properties is discussed in this study.