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- Jacques Lacan - French psychoanalyst, psychiatrist, and doctor involved in the psychoanalytic movement (Collège Stanislas in Paris)
- La Condamine - French geographer and mathematician (Jesuit College of Louis-le-Grand in Paris)
- Maria Elena Lagomasino - CEO of JP Morgan Private Bank from 2001 to 2005 (Fordham University)
- Philippe de La Hire - French mathematician
- Jérôme Lalande - French astronomer (Jesuit College in Lyon)
- Alexander Graf Lambsdorff - German politician
- Mario Armando Lavandeira Jr. - Cuban-American celebrity gossip blogger who writes under the pseudonym Perez Hilton (Belen Jesuit in Miami, Florida)
- Francesco Lana de Terzi - Italian aeronautics pioneer (studied under Athanasius Kircher)
- Charles Laughton - English Academy Award-winning stage and film actor, screenwriter, and producer (Stonyhurst College)
- Cecilia Landerreche - Director of the DIF (Universidad Iberoamericana)
- John Leahy - Chief Operating Officer of Airbus (Fordham University)
- Timothy Leary - American psychologist and writer (expelled from College of the Holy Cross, Worcester, Massachusetts after his freshman year)
- Jordhy Ledesma - Dominican web architect and poet (Instituto Politecnico Loyola)
- Byron Lee - Jamaician music pioneer (St. George's College, Jamaica)
- Anthony James Leggett - British professor of physics (Wimbledon College)
- Georges Lemaître - Belgian priest and astronomer (Collège du Sacré Coeur, Charleroi, Belgium)
- Elmore Leonard - American novelist (University of Detroit Jesuit High School and University of Detroit)
- Pietro Leoni - Italian priest of the Russian Catholic Church, survivor of the GULAG, author of Spio dei Vaticano. (Collegium Russicum)
- G. Gordon Liddy - American political strategist (Fordham University)
- John T. Lis - American professor of molecular biology and genetics; 2000 Guggenheim Fellow (Fairfield University)
- Vince Lombardi - Hall of Fame football coach for the Green Bay Packers (Fordham University)
- Lope de Vega - Spanish Baroque playwright and poet (Colegio Imperial de Madrid)
- Eduardo López de Romaña - President of Peru (Stonyhurst College)
- Federico García Lorca - Spanish poet and playwright (attended Jesuit school as a boy in Grenada)
- Gabriel García Márquez - Colombian author and Nobel laureate (Jesuit Colegio San Jose in Barranquilla and Jesuit College in Bogotá, Colombia)
- Henri de Lubac - French theologian (Gregorian University in Rome, Italy)
- Ruud Lubbers - former Prime Minister of the Netherlands and former United Nations High Commissioner for Refugees (Canisius College, Nijmegen, The Netherlands)
- Peter Lynch - American financial leader (Boston College, Chestnut Hill, Massachusetts)
- Patrick J. Leahy - United States Senator (Georgetown University)
- Nathan Lane - American actor (St. Peter's Preparatory High School, New Jersey)
- Bernard Lonergan - Canadian professor and theologian (Gregorian University)
- Emmanuel Lubezki - cinematographer (The Birdcage, Reality Bites and other films) (Universidad Iberoamericana)
Read more about this topic: List Of Alumni Of Jesuit Educational Institutions