An alkaliphilic actinomycete, strain AC3(T), was isolated from Lonar soda lake, in India. Based on 16S rRNA gene sequence analysis it was identified that the strain belongs to the class Actinobacteria and was most closely related to Streptomyces sodiiphilus JCM 13581(T) (96.4 % sequence similarity), Streptomyces leeuwenhoekii DSM 42122(T) (96.1 %), Streptomyces albus NRRL B-2365(T) (96.1 %), Streptomyces panacagri Gsoil 519(T) (96.0 %), Streptomyces fimbriatus NBRC 15411(T) (95.9 %) and other members of the genus Streptomyces (<95.9 %).The strain formed a well separated clade in the genus Streptomyces based on the 16S rRNA gene analysis of all of the validly named Streptomyces species. Strain AC3(T) was observed to produce light-cream substrate and white aerial mycelia on most tested media. The optimum pH for growth was determined to be 9.5-10.0 with no growth at pH 7.0. The DNA G+C content of strain AC3(T) was determined to be 71.2 mol %. The results of the polyphasic analysis allowed a clear differentiation of strain AC3(T) from all other members of the genus Streptomyces. Strain AC3(T) is thus considered to represent a novel member of the genus Streptomyces, for which the name Streptomyces alkalithermotolerans sp. nov. is proposed. The type strain is AC3(T) (=KCTC 29497(T) = JCM 30167(T)).