| Nashville Soccer Club | Major League Soccer | Nashville | 2017 | Geodis Park, Nissan Stadium |
| NBA New Basket A-Zena | — | Genova | — | — |
| New Basket Brindisi | Serie A | Brindisi | 1992 | PalaPentassuglia |
| 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 Saints | National Football League | — | 1967 | Caesars Superdome |
| New Polibasket San Bonifacio | — | — | — | — |
| New York City FC | Major League Soccer | New York | 21 maggio 2013 | Yankee 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, East Rutherford | 1960 | MetLife Stadium |
| New York Knicks | National Basketball Association | New York | 1946 | Madison Square Garden, Madison Square Garden, 69th Regiment Armory |
| New York Mets | Major League Baseball | — | 1962 | Citi Field |
| New York Red Bulls | Major League Soccer | Harrison | 1995 | Giants Stadium, Red Bull Arena |
| 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 Fiamma Stabia | — | — | — | — |
| Nuova Pallacanestro Gorizia | — | Gorizia | 1934 | — |
| Nuova Pallacanestro Vigevano | — | Vigevano | 1955 | — |
| Nuova Trogylos Priolo | — | Priolo Gargallo | 1970 | — |
| Oakland Athletics | Major League Baseball | Oakland | 1968 | Oakland-Alameda County 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 |
| Olimpia Basket Matera | — | Matera | 1960 | — |
| Olimpia Cagliari | — | Cagliari | 1953 | — |
| Olympia 68 Basketball | — | Reggio Calabria | — | — |
| Olímpico Peruano | Copa Perú | — | 2 febbraio 1945 | — |
| Oratorio Elmas | — | — | — | — |
| Orlando City Soccer Club | Major League Soccer | Orlando | 2013 | Inter&Co Stadium, Camping World Stadium |
| Orlando Magic | National Basketball Association | Orlando | 1989 | Amway Arena, Kia Center |
| Ottawa Senators | — | Kanata | 1992 | Canadian Tire Centre, TD Place Arena |
| Ottawa Senators | — | — | 1883 | — |
| Pacífico Fútbol Club | Copa Perú | — | 1949 | Stadio Iván Elías Moreno |
| Pallacanestro Ares Palermo | — | Palermo | — | — |
| Pallacanestro Aurora Desio | — | Desio | 1994 | — |
| Pallacanestro Biella | — | Biella | 1994 | Lauretana Biella Forum |
| Pallacanestro Brindisi | — | Brindisi | 1945 | PalaPentassuglia |
| Pallacanestro Cantù | Serie A | Cermenate | 1936 | palasport Pianella |
| Pallacanestro Chieti | — | Chieti | 1989 | — |
| Pallacanestro Don Bosco Livorno | — | — | — | — |
| Pallacanestro Femminile Umbertide | — | Umbertide | 2008 | — |
| Pallacanestro Ferrara 2011 | — | Ferrara | 2011 | — |
| Pallacanestro Forlì 2015 | Serie A2 | Forlì | 2015 | Unieuro Arena |
| Pallacanestro Gallaratese | — | — | — | — |