A miscarriage of justice, also known as a wrongful conviction, occurs when a person is convicted and punished for a crime that he or she did not actually commit. It can occur in both criminal and civil proceedings, which includes removal proceedings. The main contributing factors are eyewitness misidentification, faulty forensic analysis, false confessions by vulnerable suspects, perjury and lies told by witnesses, misconduct by police, prosecutors or judges and inadequate defense strategies put forward by the defendant's legal team.

The Innocence Project keeps statistics on cases where convicted defendants have subsequently been exonerated, usually by advances in the science of DNA. In many instances, wrongful convictions have not been overturned for several decades - sometimes after the innocent person has been executed, released from custody, or has died. The true prevalence of miscarriages of justice is hard to measure because many wrongful convictions are never overturned.

The term is not to be confused with "errors of impunity" which applies to cases where a guilty person goes free.