Jailtacht closely analyzes the emergence of the Irish language among republican prisoners and ex-prisoners in Northern Ireland from the 1970s to the present. This pioneering study shows how, despite the efforts of prison authorities to suppress the language, in some parts of the prison it became the exclusive language used by prisoners. Drawing on interviews with these prisoners, Diarmait Mac Giolla Chríost shows how these developments gave rise to the popular coinage of the term “Jailtacht,” a deformation of “Gaeltacht”—the official Irish-speaking district of the Republic of Ireland—to describe this unique linguistic phenomenon. He goes on to trace the dramatic impact this politically rooted adoption of the language had on Irish society both at the time and in the subsequent decades.