The Cape Floristic Region (CFR) of South Africa is globally recognized for its exceptional biodiversity and endemism, but despite extensive floral studies, its phytophagous insect fauna remains poorly studied. Here, we employ an integrative taxonomic approach including macro- and micro-photography, micro-CT scanning, scanning electron microscopy, and multigene molecular phylogenetics to describe a recently discovered, morphologically and genetically distinct lineage of geometrid moths (Lepidoptera: Geometridae) from the CFR, comprising a new genus, Fynbosia Englund, Staude & Sihvonen, gen. nov. and two new species, F. horingaria Englund, Staude & Sihvonen, sp. nov. and F. unicaria Englund, Staude & Sihvonen, sp. nov. Morphological and molecular evidence support the placement of Fynbosia gen. nov. within the subfamily Larentiinae but suggest no close affiliation to any described tribe. The new genus appears to be endemic to the CFR's montane fynbos and renosterveld vegetation types, which may act as ecological islands that foster speciation. The discovery underscores the overlooked insect diversity of the region and the urgent need for more comprehensive surveys. Our findings contribute to a better understanding of geometrid diversity and highlight the value of integrative taxonomy and non-destructive imaging in documenting rare and cryptic lineages.