A Gram-positive aerobic actinomycete, designated SR14.14(T), isolated from the rhizospheric soil of rubber tree was determined taxonomically using a polyphasic approach. The organism contained meso-diaminopimelic acid and the N-acetyl type of peptidoglycan. The predominant menaquinones were MK-9, MK-9(H₂) and MK-9(H₄). Madurose was detected in the whole-cell hydrolysates. Mycolic acids were not presented. Major phospholipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol mannoside. Major cellular fatty acid was iso-C(₁₆:₀) and the G+C content was 71.9 mol %. Phylogenetic analysis based on 16S rRNA gene sequence suggested that the isolate belongs to the genus Sphaerisporangium. The sequence similarity value between the strain SR14.14(T) and its closely related species, Sphaerisporangium album, was 97.8%. DNA-DNA hybridization values between them were well below 70%. Based on genotypic and phenotypic data, strain SR14.14(T) represents a novel species in the genus Sphaerisporangium, for which the name Sphaerisporangium siamense sp. nov. is proposed. The type strain is SR14.14(T) (=BCC 41491(T)=NRRL B-24805(T)=NBRC 107570(T)).