The Prix Iris for Best Cinematography in a Documentary (French: Prix Iris de la meilleure direction de la photographie d'un long métrage documentaire) is an annual film award, presented by Québec Cinéma as part of its Prix Iris awards program, to honour the year's best cinematography in documentary films made within the Cinema of Quebec.
The award was presented for the first time at the 19th Quebec Cinema Awards in 2017.
With his win for Mother Saigon (Má Sài Gòn), Mathieu Laverdière became the first cinematographer to receive an award for Best Cinematography in a Documentary and Best Cinematography, having previously won for Underground (Souterrain).