A new species of the genus Anax, A. aurantiacus, is described and illustrated based on adults of both sexes and exuviae from Thailand. This new species was previously considered by several authors to be a form of A. immaculifrons Rambur, 1842, but was never officially described. Anax aurantiacus sp. nov. is differentiated from A. immaculifrons based on coloration and morphological differences in the adults and larvae. Two species delimitation analyses (ABGD and bPTP) were also carried out, from which can be inferred that A. aurantiacus and A. immaculifrons were different Molecular Operational Taxonomic Units. Material and images available on internet and literature show the species to be present in Cambodia, Laos, China, Hong Kong, Thailand, and Vietnam, with A. immaculifrons occurring in South Asia and further west. Anax immaculifrons therefore needs to be deleted from the checklists from Cambodia, Laos, China, Hong Kong, Thailand, and Vietnam, replaced by A. aurantiacus sp. nov.