We live in a time of unprecedented environmental change, with climate change, habitat alteration, pollution, invasive species and over-exploitation all contributing to species declines. Biodiversity researchers, policy workers, and site and species managers work to stem the tide of declines. Museum collections play a key role, or could play a key role, through supporting biodiversity and nature conservation-related research, management and policy; they also support public education about biodiversity, although that is not the focus of this booklet. This booklet explores some of the problems biodiversity faces, and examples of how UK museum collections can help biodiversity workers meet these challenges. It presents some results from a study funded by the British Ecological Society in 2018–19, which aimed to develop a strategic approach to using UK museum collections to support biodiversity conservation.