Christian Aaron Boulogne (11 August 1962 – May 2023), also known as Ari Boulogne and Ari Päffgen, was a French photographer, actor and writer. Boulogne was born in Neuilly-sur-Seine on 11 August 1962. He was the son of German singer and actress Nico. Nico always claimed that the biological father was French actor Alain Delon, although Delon consistently denied paternity to Boulogne.

He was initially raised by his mother before he was adopted by Delon's mother, Édith, and her second husband, Paul Boulogne, whose surname he legally took. Edith Boulogne said she always knew he was her grandson. He spent most of his childhood in Bourg-la-Reine. In 2001 and 2019, Boulogne attempted to sue Delon for legal recognition of paternity, but without success. Boulogne had two children. In 2001, he published a memoir, Love Never Forgets, in which he elaborates on his relationship with his mother and his father.

Boulogne was found dead in his Paris apartment on 20 May 2023, following a heroin overdose a month before. A woman, supposedly his partner, was taken into custody for failure of duty to rescue. He was 60, and was in an advanced stage of decomposition when discovered.