This peer reviewed document reflects on the centrality of Research Infrastructures (RIs) to the Humanities. It argues that without RIs such as archives, libraries, academies, museums and galleries (and the sources that they identify, order, preserve and make accessible) significant strands of Humanities research would not be possible. After proposing a wide-ranging definition of digital RIs – with the aim of reflecting on the meaning of infrastructure in the Humanities rather than on those parts common to other domains of science – it attempts to relate physical RIs to digital ones. By drawing on a number of case studies – chosen to showcase the variety of research around existing or emerging infrastructures – it demonstrates that digital RIs offer Humanities scholars new and productive ways to explore old questions and develop new ones.