| Magika Pallacanestro | — | Castel San Pietro Terme | — | — |
| Magnolia Basket Campobasso | — | Campobasso | 2017 | — |
| Mariscal Miller | Copa Perú | — | — | Estadio Jorge Basadre |
| Mariscal Nieto de Ilo | Copa Perú | — | — | Estadio Mariscal Nieto |
| Mariscal Sucre | — | — | 1925 | National Stadium of Peru |
| Maurolico Messina | — | — | — | — |
| Maxima Roma | Serie A | — | 2026 | Palazzo dello Sport |
| Memphis Grizzlies | National Basketball Association | Memphis | 1995 | Pyramid Arena, FedExForum |
| Mercede Basket Alghero | — | Alghero | 1977 | — |
| Merchants United Social, Sports and Cultural Association | Peruvian Primera División | — | 19 September 2002 | Juan Maldonado Gamarra Stadium |
| Miami Dolphins | National Football League | Miami | 1966 | Hard Rock Stadium |
| Miami Heat | National Basketball Association | Miami | 1988 | Miami Arena, Kaseya Center |
| Miami Marlins | Major League Baseball | — | 1993 | LoanDepot Park, Hard Rock Stadium |
| Miguel Grau de Abancay | Copa Perú | — | 1955 | Estadio Monumental de Condebamba |
| Milwaukee Braves | Major League Baseball | Milwaukee | 1953 | Milwaukee County Stadium |
| Milwaukee Brewers | Major League Baseball | Milwaukee | 1969 | American Family Field |
| Milwaukee Bucks | National Basketball Association | Milwaukee | 1968 | UW–Milwaukee Panther Arena, Bradley Center, Fiserv Forum |
| Mina San Vicente | Copa Perú | — | June 1970 | — |
| Minnesota North Stars | — | Bloomington | 1967 | Met Center |
| Minnesota Timberwolves | National Basketball Association | Minneapolis | 1989 | Hubert H. Humphrey Metrodome, Target Center |
| Minnesota Twins | Major League Baseball | — | 1901 | Target Field, American League Park, Metropolitan Stadium, Hubert H. Humphrey Metrodome, Boundary Field, Griffith Stadium |
| Minnesota United FC | Major League Soccer | Minneapolis | 2015 | Allianz Field, Huntington Bank Stadium |
| Minnesota Wild | — | Saint Paul | 2000 | Grand Casino Arena |
| Miraflores Sporting Club | — | — | — | Estadio Nacional del Perú (1897) |
| Modena Basket | — | — | — | — |
| Montigarda Basket | — | Montichiari | — | — |
| Montreal Canadiens | — | — | 1909 | Bell Centre, Jubilee Arena, Montreal Forum, Montreal Arena, Mount Royal Arena |
| Montreal Expos | Major League Baseball | — | 1969 | Olympic Stadium, Jarry Park Stadium |
| Montreal Maroons | — | — | 1924 | Montreal Forum |