In this paper, we present an original database characterizing the prison conditions of all 187 active prisons in France. Our database, called PCiF, aggregates data from both public and restricted-access sources and captures key dimensions of prison conditions: age of the facility, geographical isolation, prison size, occupancy rate, prison guard workload, access to family visiting rooms, in-prison work, complaints to the national prison inspectorate, and suicide. We also propose a synthetic index ranging from 0 to 100, based on between-prison rankings, to measure the overall quality of prison conditions within each facility. We validate our Prison Conditions Index by confronting it with emergency reports as well as judicial sanctions issued against French prisons. Such data is not only useful to document disparities in prison conditions through France, but also as a prerequisite to study their influence on different stakeholders, e.g. prisoners and judges.