Conservation resources are limited, making it impossible to invest equally in all threatened species. One way to maximise conservation gains is to focus upon those species with particular public appeal, using them to generate funding and support that could also benefit additional, less charismatic species. Although this approach is already used by many conservation organisations, no reliable metrics currently exist to determine the likely charisma of a given species, and therefore identify the most appropriate targets for such campaigns. Here we use market research techniques on over 1500 people from five continents to assess the relative charisma of different mammals, which factors appear to drive it, and which species show unexpectedly high or low charisma. Highly favoured species were associated with striking colouration, large body size, carnivory and high IUCN threat status. The public preferred species with which they had affinity and familiarity, and show distinct preferences for large and threatened species of mammals in comparison to their less charismatic counterparts. Australian respondents in this survey stand out as exceptions. While clearly liking two charismatic felids in common with other survey respondents from around the world, Australians ranked species from their own region (Australia and South East Asia) more highly than did respondents in other regions.