A private investigator (often abbreviated to PI and informally called a private eye), a private detective, or inquiry agent, is a person who can be hired by individuals or groups to undertake investigatory law services. Private investigators often work for attorneys in civil and criminal cases. 

In 1833, Eugène François Vidocq, a French soldier, criminal, and privateer, founded the first known private detective agency, “Le Bureau des Renseignements Universels pour le commerce et l’Industrie” (“The Office of Universal Information For Commerce and Industry”) and hired ex-convicts. Official law enforcement tried many times to shut it down. In 1842, police arrested him in suspicion of unlawful imprisonment and taking money on false pretences after he had solved an embezzlement case. Vidocq later suspected that it had been a set-up. He was sentenced to five years and fined 3,000 francs, but the Court of Appeals released him. Vidocq is credited with having introduced record-keeping, criminology, and ballistics to criminal investigation. He made the first plaster casts of shoe impressions. He created indelible ink and unalterable bond paper with his printing company. His form of anthropometrics is still partially used by French police. He is also credited for philanthropic pursuits – he claimed he never informed on anyone who had stolen for real need.