| 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 |
| Napoli Basket | Serie A | Naples | 2016 | PalaBarbuto |
| Napoli Basket Vomero | — | Naples | 1986 | — |
| Nashville Predators | — | — | 1998 | Bridgestone Arena |
| Nashville SC | Major League Soccer | Nashville | 2017 | Geodis Park, Nissan Stadium |
| New Basket Palestrina | — | — | — | — |
| New England Patriots | National Football League | Foxborough | 1959 | Gillette Stadium |
| New England Revolution | Major League Soccer | Foxborough | 1995 | Gillette Stadium |
| New Jersey Devils | — | Newark, East Rutherford | 1974 | Meadowlands Arena, Prudential Center |
| New Orleans Pelicans | National Basketball Association | New Orleans | 2002 | Paycom Center, Smoothie King Center |
| New Polibasket San Bonifacio | — | — | — | — |
| New York City FC | Major League Soccer | New York City | 21 May 2013 | Yankee Stadium |
| New York Giants | National Football League | New York metropolitan area | 1925 | MetLife Stadium |
| New York Giants | — | — | — | — |
| New York Islanders | — | Brooklyn, Elmont, Uniondale | 1972 | UBS Arena, Barclays Center, Nassau Veterans Memorial Coliseum |
| New York Jets | National Football League | New York City, East Rutherford | 1960 | MetLife Stadium |
| New York Knicks | National Basketball Association | New York City | 1946 | Madison Square Garden, Madison Square Garden, 69th Regiment Armory |
| New York Mets | Major League Baseball | — | 1962 | Citi Field |
| New York Rangers | — | Manhattan | 1926 | Madison Square Garden, Madison Square Garden |
| New York Yankees | Major League Baseball | The Bronx | 1903 | Yankee Stadium, Yankee Stadium, Hilltop Park, Shea Stadium, Polo Grounds |
| Nova Virtus Ragusa | — | Ragusa | — | — |
| NPC Rieti | — | Rieti | 2011 | — |
| Nuova AMG Sebastiani Basket Napoli | — | Rieti | 1946 | — |
| Nuova Fiamma Stabia | — | — | — | — |
| Nuova Pallacanestro Gorizia | — | Gorizia | 1934 | — |
| Nuova Pallacanestro Vigevano | — | Vigevano | 1955 | — |
| Oakland Athletics | Major League Baseball | Oakland | 1968 | Oakland Coliseum |
| OBG Roma | — | — | — | — |
| Octavio Espinosa de Ica | Copa Perú | — | 1923 | Estadio José Picasso Peratta |
| Oklahoma City Thunder | National Basketball Association | Oklahoma City | 2008 | Climate Pledge Arena, Tacoma Dome, Paycom Center, Kingdome |
| Oleggio Magic Basket | — | Oleggio | — | — |
| Olimpia Basket Matera | — | Matera | 1960 | — |
| Olimpia Basket Pistoia | — | Pistoia | 1965 | — |
| Olimpia Milano | Serie A | Milan | 1936 | Forum di Milano |
| Olympia 68 Basketball | — | Reggio Calabria | — | — |
| Olímpico Peruano | Copa Perú | — | 2 February 1945 | — |
| Oratorio Elmas | — | — | — | — |
| Orlandina Basket | — | Capo d'Orlando | 1978 | PalaFantozzi |
| Orlando City SC | Major League Soccer | Orlando | 2013 | Inter&Co Stadium, Camping World Stadium |
| Orlando Magic | National Basketball Association | Orlando | 1989 | Amway Arena, Kia Center |
| Orzi Basket | — | Orzinuovi | 1964 | — |
| Ottawa Senators | — | Kanata | 1992 | Canadian Tire Centre, TD Place Arena |
| Ottawa Senators | — | — | 1883 | — |
| Pallacanestro Aurora Desio | — | Desio | 1994 | — |
| Pallacanestro Biella | — | Biella | 1994 | BiellaForum |
| Pallacanestro Broni 93 | — | — | — | — |