Philiris diana Waterhouse & Lyell, 1914 from the Wet Tropics of northeastern Queensland was previously thought to be monotypic, being most closely related to Philiris papuanus Wind & Clench, 1947 from Cape York Peninsula, Australia, and mainland New Guinea. However, a new subspecies was recently discovered on the Atherton Tableland, which we illustrate, diagnose and describe as Philiris diana fortuna ssp. nov. It appears to be a narrow-range endemic, restricted to montane forest (750–1,090 m asl) and allopatric or parapatric from the nominotypical subspecies Philiris diana diana Waterhouse & Lyell, 1914, which is largely restricted to low to mid-altitude forests in the coastal escarpment in the Cairns-Kuranda district. Despite being separated by a minimum distance of only 20–25 km, the two taxa show substantial phenotypic differences in wing pattern elements, but negligeable differences according to the mitochondrial COI barcode region (mean p-distance = 0.28%). The habitat and biology of the new taxon are summarized, and likely historical processes driving divergence between upland and lowland populations of this species hypothesized.