The conservation of our planet's biodiversity is a global priority. This was recognised in 1992 when 150 countries signed the United Nations Convention on Biological Diversity in Rio de Janeiro. Central to biodiversity conservation is an understanding of biodiversity itself which requires answering the questions of how many species we have, how they are related, and where they are distributed. And for this, we need taxonomists who discover, describe, and identify the diversity of life. The work of taxonomists underpins biological sciences and is fundamental in managing biodiversity. Australian marine life is both incredibly diverse and poorly known, with new species being continually discovered and named. A name provided by a taxonomist is a key to information about species distributions, ecology, reproduction, and genetic diversity, but only if the correct name is used. Thus, it is critically important that species are correctly identified. Taxonomists are instrumental in recognising introduced species arriving on our shores, determining whether management plans for marine protected areas are effective, and assessing the impact of climate change on marine life. We stress the importance of collections-based research in the fight against biodiversity loss and climate change and the need for collaboration between end users and taxonomists.