Léonie Duquet (1916, Longemaison, Doubs – 1977) was a French nun who was killed by the military regime of Argentine President Jorge Rafael Videla during the Dirty War.
Léonie Duquet dedicated most of her life to religion, becoming interested in the Catholic ministry when she was young. She joined the Catholic Church in France, and, after taking vows as a nun, she traveled to many countries, on many church-related missions.
Duquet and fellow nun Alice Domon arrived in Argentina at some point during the early 1970s. Duquet dedicated herself to helping Argentina's poor, and became involved with the Mothers of the Plaza de Mayo movement. This enraged the authorities. Argentina was under a military government at the time, and many Argentine citizens that opposed the government were killed or officially 'disappeared'.
Duquet lived and worked at the San Pablo de Ramos Mejia cathedral. In December 1977, she was arrested by Alfredo Astiz. Alfredo Astiz had arrested and given orders to kill Mothers of Plaza de Mayo organizer Azucena Villaflor, and he did not want any witnesses. Leone Duquet was killed by a death squad that the Argentine dictatorship had at the time.