A debtors' prison is a prison for people who are unable to pay debt. Through the mid-19th century, debtors' prisons (usually similar in form to locked workhouses) were a common way to deal with unpaid debt in Western Europe. Destitute persons who were unable to pay a court-ordered judgment would be incarcerated in these prisons until they had worked off their debt via labour or secured outside funds to pay the balance. The product of their labour went towards both the costs of their incarceration and their accrued debt. Increasing access and lenience throughout the history of bankruptcy law have made prison terms for unaggravated indigence obsolete over most of the world.

Since the late 20th century, the term debtors' prison has also sometimes been applied by critics to criminal justice systems in which a court can sentence someone to prison over willfully unpaid criminal fees, usually following the order of a judge. For example, in some jurisdictions within the United States, people can be held in contempt of court and jailed after willful non-payment of child support, garnishments, confiscations, fines, or back taxes. Additionally, though properly served civil duties over private debts in nations such as the United States will merely result in a default judgment being rendered in absentia if the defendant willfully declines to appear by law, a substantial number of indigent debtors are legally incarcerated for the crime of failing to appear at civil debt proceedings as ordered by a judge. In this case, the crime is not indigence, but disobeying the judge's order to appear before the court. Critics argue that the "willful" terminology is subject to individual mens rea determination by a judge, rather than statute, and that since this presents the potential for judges to incarcerate legitimately indigent individuals, it amounts to a de facto "debtors' prison" system.