This chapter examines the relationship that museums have developed with their audiences, and undertakes a brief history of the development of that role. It draws examples from museum marketing in four Commonwealth countries: the UK, Australia, New Zealand and Canada, which have a similar history and funding approach. One of the most serious issues facing museum marketers today is the erosion in the proportion of revenue provided by government, which needs to be supplemented by audience revenue and giving from individuals and trusts. This tripartite funding model – government, audience and ‘sponsor ’ income – is essential to museum sustainability. The erosion of government income gives marketing a boost, as it becomes an important tool for helping to fill the funding gap left by declining government revenue. This chapter contributes to understanding the relative value of140 different types of audiences to museums. Audiences are important, especially when government support is reduced and the arts are both pressured to be more business-like and more attune to the needs of diverse audiences.