Investigation of a Citizen Above Suspicion (Italian: Indagine su un cittadino al di sopra di ogni sospetto) is a 1970 Italian satirical crime thriller film directed by Elio Petri, starring Gian Maria Volonté and Florinda Bolkan. It is a psychological, black-humored satire on corruption in high office, telling the story of a top police officer who kills his mistress, and then tests whether the police would charge him for this crime. He begins manipulating the investigation by planting obvious clues while the other police officers ignore them, either intentionally or not.

The film was released in Italy by Euro International Pictures on 9 February 1970, to widespread acclaim from critics. It won the Jury Prize at the 1970 Cannes Film Festival, and the David di Donatello Awards for Best Film for Best Actor (Gian Maria Volonté). In the United States, it won the Oscar for Best Foreign Language Film. Petri and his co-writer Ugo Pirro were nominated for Best Original Screenplay.

In 2008, the film was included on the Italian Ministry of Cultural Heritage’s 100 Italian films to be saved, a list of 100 films that "have changed the collective memory of the country between 1942 and 1978."