Between steam and cybernetics lies a missing phase in the history of information culture. Beginning in the late nineteenth century, national governments and writers of fiction alike began to take an interest in information not simply as fact, nor yet as effortlessly transmissible data, but as an unusual and destabilizing new phenomenon. For some writers, such as Joseph Conrad and Walter Benjamin, 'information' came to represent not effortless transmissibility, but rather an interruption of meaningful communication. For others - such as Elizabeth Bowen - such interruptions were themselves ways of making new kinds of meaning. The attempt to reimagine and redefine information produced a range of new informatic phenomena dedicated to its control: passports, files, and identity papers; the files of Mass-Observation movement; the literal and figurative blackout procedures of the Blitz; and the government-backed 'information film'. Modernist Informatics traces the effects of these new phenomena in early twentieth-century culture, where experimental approaches to narrative and to subjectivity began to compete with government archives for the right to represent the citizens of the modern security state. It argues that information and literary narrative have a history of entanglement as well as antagonism, and that this double relation was central to the cultural shaping of modernity.