Constituting almost 7% of the world’s extant mammals, marsupials predominate in the Australasian region and are also present in the Americas. The 300 or so species of living marsupials show astonishing variation in size, behaviour, ecology and exploit virtually all terrestrial environments. Recent studies on the phylogenetic systematics of marsupials have done much to clarify the relationships of both extant and extinct forms but several controversial problems remain. With the Natural History Museum collection being one of the main reference collections for research on this group, there is a clear need to make this resource available as widely as possible so taxonomy, ecology and conservation researchers can access this unique resource. The marsupial collection of the Natural History Museum contains circa 500 primary type specimens. This richness of specimens is largely due to the accessions of Australian mammals formed by Mr John Gould, and other notable donors of specimens include Lord Derby, Dr G Bennett, Messrs O Salvin, F D Goodman, John Macgillivray and F R Rayner. M R Oldfield Thomas also contributed significantly to marsupial taxonomy and privately financed collecting expeditions to South America that resulted in the acquisition and description of several new marsupial species. In light of this, the Natural History Museum supported an initiative to digitise this collection, photographing and data-basing all of this material so it can be made available on the web through the NHM Data Portal.