| New York Mets | Grandes Ligas de Béisbol | — | 1962 | Citi Field |
| New York Rangers | — | Manhattan | 1926 | Madison Square Garden (1925), Madison Square Garden |
| New York Yankees | Grandes Ligas de Béisbol | El Bronx | 1903 | Yankee Stadium, Yankee Stadium, Hilltop Park, Shea Stadium, Polo Grounds |
| Nordiques de Québec | — | — | 1972 | Colisée de Québec |
| Nova Virtus Ragusa | — | Ragusa | — | — |
| NPC Rieti | — | Rieti | 2011 | — |
| Nuova Fiamma Stabia | — | — | — | — |
| Nuova Pallacanestro Vigevano | — | Vigevano | 1955 | — |
| Nuova Sebastiani Basket Rieti | — | Rieti | 1946 | — |
| Oakland Athletics | Grandes Ligas de Béisbol | Oakland | 1968 | Oakland Coliseum |
| OBG Roma | — | — | — | — |
| Oklahoma City Thunder | National Basketball Association | Oklahoma City | 2008 | Climate Pledge Arena, Tacoma Dome, Paycom Center, Kingdome |
| Olimpia Basket Matera | — | Matera | 1960 | — |
| Olimpia Basket Pistoia | — | Pistoya | 1965 | — |
| Olimpia Cagliari | — | Cagliari | 1953 | — |
| Olímpico Peruano | Copa Perú | — | 2 de febrero de 1945 | — |
| Oratorio Elmas | — | — | — | — |
| Orlandina Basket | — | Capo d'Orlando | 1978 | PalaFantozzi |
| Orlando City Soccer Club | Major League Soccer | Orlando | 2013 | Inter&Co Stadium, Estadio Citrus Bowl |
| Orlando Magic | National Basketball Association | Orlando | 1989 | Amway Arena, Kia Center |
| Ottawa Senators | — | Kanata | 1992 | Canadian Tire Centre, TD Place Arena |
| Padres de San Diego | Grandes Ligas de Béisbol | San Diego | 1969 | Petco Park |
| Pallacanestro Ares Palermo | — | Palermo | — | — |
| Pallacanestro Biella | — | Biella | 1994 | BiellaForum |
| Pallacanestro Brindisi | — | Bríndisi | 1945 | PalaPentassuglia |
| Pallacanestro Broni 93 | — | — | — | — |
| Pallacanestro Cantù | Lega Basket Serie A | Cermenate | 1936 | Palasport Pianella |
| Pallacanestro Don Bosco Livorno | — | — | — | — |
| Pallacanestro Ferrara 2011 | — | Ferrara | 2011 | — |
| Pallacanestro Gallaratese | — | — | — | — |
| Pallacanestro Interclub | — | — | — | — |
| Pallacanestro Lago Maggiore | — | — | — | — |
| Pallacanestro Livorno | — | Livorno | — | — |
| Pallacanestro Lucca | — | Lucca | — | — |
| Pallacanestro Mantovana | — | Mantua | 2004 | — |
| Pallacanestro Messina | — | Mesina | 1976 | — |
| Pallacanestro Orzinuovi | — | Orzinuovi | 1964 | — |
| Pallacanestro Patti | — | — | — | — |
| Pallacanestro Piacentina | — | Piacenza | 2011 | — |
| Pallacanestro Pozzuoli | — | — | — | — |
| Pallacanestro Reggiana | Lega Basket Serie A | Reggio Emilia | 1974 | PalaBigi |
| Pallacanestro Ribera | — | — | 1969 | — |
| Pallacanestro Sant'Antimo | — | Sant'Antimo | 1989 | — |
| Pallacanestro Senigallia | — | Senigallia | — | — |
| Pallacanestro Treviso | Lega Basket Serie A | Treviso | 1954 | Palaverde |
| Pallacanestro Trieste | Lega Basket Serie A | Trieste | 1975 | Palatrieste |
| Pallacanestro Varese | Lega Basket Serie A | Varese | 1945 | PalaWhirlpool |
| Pallacanestro Virtus Cassino | — | Frosinone | 2011 | — |