This dissertation brings the quotidian reality of early modern London prisons to bear on the plays of Shakespeare and his contemporaries. It presents the range of spheres in which prison language operated, describing a continuum between the performances of real imprisonment in the streets, the staging of London prison scenes, and the words and metaphors of imprisonment in Shakespeare's plays. The first chapter presents London's prisons as local, even domestic, habitations, physically integrated into the city itself and contributing to the sights, sounds and smells of the streets. The second analyses their portrayal in non-dramatic literature, where they become remote and infernal locations, seas, ships, islands and universities. It argues that these metaphors find coherence in a counter-utopian description of one of the Counter prisons, and applies these findings to the prison scene in Richard II. Chapter three addresses the plays which staged named London prisons at the beginning of the seventeenth$ entury. It discerns domestic, utopian and infernal strains, and analyses the prison scenes themselves as sites of performance and metatheatrical departure, arguing that the performative elements of local imprisonment are recognisable in these dramatic prisons as the boundaries of the stage prison are elided with those of the play itself. These findings are applied to Measure for Measure, which is located within the progression of London prison plays. The final two chapters explore prison language and actual imprisonment in Shakespearean tragedy and romance. In the tragedies, prison metaphors vie for effective control, as language is both restricted and made eloquent by the state of imprisonment. In Shakespeare's romances, prison words cause actual imprisonment beyond their speakers' control. Foucault marginalised the role of the early modern prison system in his genealogy of modern imprisonment. Literary critics in the last thirty years have followed his lead. This dissertation reclaims London's prisons as a vital context for the plays of Shakespeare and his contemporaries.