In this paper we provide the oldest evidence of termites in Australia, based on an aggregation of several hundred morphologically distinctive faecal pellets preserved as opalized casts from the Griman Creek Formation (Albian-Cenomanian: c. 100 Ma) at Lightning Ridge, New South Wales, Australia. This trace fossil extends the record of isopterans in Australia around 40 to 50 million years earlier than previously identified termite wing impressions, and indicates that this group was an active component of the detritivorous community in eastern Gondwanan terrestrial ecosystems by the mid-Cretaceous. The distinctive prismatic faecal pellets with hexagonal cross-sections (referable to Microcarpolithes hexagonalis Vangerow) were probably produced by kalotermitid or mastotermitid termites. The associated fossil plant assemblage indicates that the producers of the faecal pellets likely fed on conifer wood. Based on the distribution of extant termites, the climate of the Lightning Ridge area (Surat Basin) was probably warm and moist during the mid-Cretaceous. Recognition that termites were well established in Australian terrestrial ecosystems by the Albian-Cenomanian implies that vicariance may have been just as influential as trans-oceanic dispersal in determining the early distribution of major termite clades. Opalization of these delicate faecal pellets highlights the potential for further discoveries of three-dimensionally preserved soft or friable body and trace fossils in the Lightning Ridge opal deposits.