| Loubser, Susan | Kinematics and stellar populations in brightest cluster galaxies | 2009 | University of Central Lancashire | GMOS-N/GMOS-S | UK |
| Lorenzo-Oliveira, Diego | Cronometros Estelares: Calibrando a Atividade Cromosferica em Estrelas de Baixa Massa | 2016 | Federal University of Rio de Janeiro | GMOS-N | Brazil |
| Lopez Rodriguez, Enrique | A total and polarized infrared flux view of the AGN clumpy torus | 2013 | University of Florida | NIRI/MICHELLE/TRECS | USA |
| Longstaff, Emma S. | The irradiated atmospheres of brown dwarf companions to white dwarf stars | 2019 | University of Leicester | GNIRS | UK |
| Longmore, Steven Neil | The cradle of galactic superpowers: studying the natal environment of massive stars | 2007 | University of New South Wales | MICHELLE | Australia |
| Lloyd, James Patrick | The detection and characterization of low mass companions to sun-like stars | 2002 | University of California, Berkeley | Hokupaa | USA |
| Livermore, Rachael | Harnessing the Power of Gravitational Lensing: Resolved Star Formation at Redshift 1 - 4 | 2013 | Durham University | NIFS | UK |
| Liu, Xin | Observations of galaxies harboring active massive black holes: the curious case of binaries and the coupled growth of black holes and their hosts | 2010 | Princeton University | GMOS-N | USA |
| Liu, Tingting | The Search for Supermassive Black Hole Binaries in the Time Domain | 2018 | University of Maryland | GMOS-S | USA |
| Liskowsky, Joseph Paul | Planet formation in transition disks: modeling, spectroscopy, and theory | 2012 | Clemson University | PHOENIX | USA |
| Limoges, Marie-Michele | Releve spectroscopique et etude des proprietes physiques des etoiles naines blanches a moins de 40 parsecs du Soleil | 2014 | Universite de Montreal | GMOS-N/GMOS-S | Canada |
| Li, Dan | High-angular resolution mid-infrared study of disks and environments of young stars | 2013 | University of Florida | MICHELLE/TRECS | USA |
| Levitan, David B. | Finding needles in the haystack: a search for AM CVn systems using the Palomar Transient Factory | 2013 | California Institute of Technology | GMOS-N | USA |
| Lena, Davide | Aspects of supermassive black hole growth in nearby active galactic nuclei | 2015 | Rochester Institute of Technology | GMOS-S | USA |
| Lawton, Brandon | Diffuse interstellar bands in damped Lyman-alpha and starburst galaxies | 2008 | New Mexico State University | GMOS-S | USA |
| Lavigne, Jean-Francois | Imagerie a haut contraste et caracterisation d'exoplanetes par la spectroscopie integrale de champ | 2009 | Universite de Montreal | NIFS+ALTAIR | Canada |
| Lau, Marie Wingyee | Quasars Probing Quasars: The Circumgalactic Medium Surrounding Z 2 Quasars | 2017 | University of California Santa Cruz | NIRI/GNIRS | USA |
| Lansbury, George | A hard X-ray view of the distant active galactic nucleus population with NuSTAR | 2016 | Durham University | GMOS-S | UK |
| Lamareille, Fabrice | Cosmological evolution of the physical properties of galaxies | 2006 | Laboratoire d'Astrophysique de l'Obbservatoire Midi-Pyrenees (France) | GMOS-N | Other |
| Lagos, Patricio | Distribuição espacial das populações estelares e o meio interestelar nas galáxias HII | 2008 | Observatorio Nacional | GMOS-S | Brazil |
