Phylum Cnidaria is the most ancient, venomous lineage and is defined by the presence of nematocysts, specialised intracellular capsules, which act as single-use venom delivery systems. Like other cnidarians, sea anemones utilise venom for prey capture, defence against predators and intraspecific combat1. While only 256 of their toxins have been identified in the manually annotated ToxProt database2, numerous sea anemone toxins have successfully been employed as molecular tools and candidates of pharmacological development 3. Based on the success of previously isolated toxins, we have chosen to investigate the uncharacterised sea anemone 8 toxin family in two Australian sea anemone species using long-read genome sequencing in conjunction with tissue specific transcriptomic datasets. Actinia tenebrosa and Telmatactis stephensoni are from superfamilies Actinioidea and Metridioidea respectively. While a draft genome assembly is available for A. tenebrosa, genome sequencing has not been undertaken for any member of the Telmatactis genus. We found an expansion of the sea anemone 8 toxin family in T. stephensoni and that the genes encoding these peptides were clustered in the genome. Additionally, sea anemone 8 toxin genes are highly expressed in envenomating tissues and were highly abundant in the milked venom of T. stephensoni. We find that the cysteine framework of sea anemone 8 toxins closely resembles that of ShK, whose synthetic analogue is about to commence phase 2 trials for the treatment of autoimmune diseases3. We conclude that the sea anemone 8 toxin family is a high copy number gene family that has been largely overlooked as there is currently a strong taxonomic and biogeographic bias in the species examined for peptide toxins, with the majority coming from the northern hemisphere and the family Actiniidae.