| Loubser, Susan | Kinematics and stellar populations in brightest cluster galaxies | 2009 | University of Central Lancashire | GMOS-N/GMOS-S | UK |
| MacArthur, Lauren Anne | Stellar populations in spiral galaxies: Broadband versus spectroscopic viewpoints | 2005 | The University of British Columbia | GMOS-N | Canada |
| Mace, Gregory Nathan | Investigating low-mass binary stars and brown dwarfs with near-infrared spectroscopy | 2014 | University of California Los Angeles | GNIRS | USA |
| Madrid, Juan Pablo | Structural parameters of compact stellar systems | 2013 | Swinburne University of Technology | GMOS-N | Australia |
| Maia, Francisco Ferreira de Souza | Characterization and structural evolution of Galactic open clusters | 2012 | Universidade Federal de Minas Gerais | GMOS-S | Brazil |
| Malo, Lison | Recherche et caracterisation des etoiles jeunes de faible masse dans le voisinage solaire | 2014 | Universite de Montreal | PHOENIX | Canada |
| Marble, Andrew Robert | QSO pairs and the Lyman-alpha forest: observations, simulations, and cosmological implications | 2007 | The University of Arizona | GMOS-S | USA |
| Marinas, Naibi | Mid-infrared high resolution imaging of Herbig Ae/Be stars: Exploring the geometry of circumstellar dust | 2007 | University of Florida | MICHELLE/TRECS | USA |
| Marois, Christian | La recherche de naines brunes et d'exoplanetes: Developpement d'une technique d'imagerie multibande | 2004 | Universite de Montreal | NIRI | Canada |
| Marshall, Brandon | An examination of the environments impacted by high-mass stars and their formation | 2018 | Iowa State University | GNIRS | USA |
| Marshall, Charlotte C. M. | On the diffuse interstellar bands and the local interstellar medium | 2017 | University of Nottingham | GNIRS | UK |
| Mast, Damian | La region central de M83 | 2008 | Universidad Nacional de Cordoba | NIRI/CIRPASS/GMOS-S | Argentina |
| Matharu, Jasleen Kaur | A Study on Quenching and Galaxy Growth in z~1 Clusters using HST WFC3 Grism Observations | 2019 | University of Cambridge | GMOS-N/GMOS-S | UK |
| May, Daniel | Propriedades de núcleos ativos de galáxias observadas no infravermelho próximo com óptica adaptativa | 2016 | University of Sao Paulo | NIFS+LGS/GMOS-N | Brazil |
| Mazzalay, Ximena | Los parsecs mas internos de las galaxias activas | 2010 | Universidad Nacional de Cordoba | NIFS+ALTAIR | Argentina |
| McConnell, Nicholas James | Black hole masses in nearby brightest cluster galaxies | 2012 | University of California, Berkeley | GMOS-N | USA |
| Mehner, Andrea | Exploring and Modeling High-excitation Emission in the Ejecta and the Wind of Eta Carinae | 2011 | University of Minnesota | GMOS-S | USA |
| Melis, Carl Anthony | The life, death, and composition of exoterrestrial planets around intermediate mass stars | 2009 | University of California, Los Angeles | NIRI/MICHELLE/TRECS | USA |
| Menezes, Roberto Bertoldo | Espectroscopia 3D de núcleos ativos de galáxias tratamento e análise de dados no óptico e no infravermelho próximo | 2012 | University of Sao Paulo | GMOS-N/GMOS-S/NIFS+ALTAIR | Brazil |
| Mentuch, Erin | Extragalactic stellar populations in the near and mid-infrared: 1-30 mum emission from evolved populations, young and dustry star forming regions and the earliest stellar populations | 2010 | University of Toronto | GMOS-N | Canada |
