Are you a prison officer who feels nervous about dealing with Muslims on the wings? Are you a prison chaplain who wants to know how your chaplaincy affects the lives of prisoners? Are you a policymaker who needs a robust base of evidence for Islam in prison? Are you an academic or a journalist seeking ground-breaking social science in a contentious field? Based on original evidence from 279 Muslim prisoners and 79 prison officers, we explore how Muslims come to be incarcerated, how the practice of Islam affects prison life and rehabilitation, the types of Islam and the effects of Islamic conversion in prison and the professional practice of officers and chaplains. We also investigate the common belief that incarceration fosters Islamist extremism and suggest improvements to faith provision and rehabilitative opportunities for Muslim prisoners.