| Onekaka Links Golf Club | Onekaka | Tasman |  New Zealand | inactive |
| Oneonta Country Club | Oneonta | New York |  United States of America | inactive |
| Oneota Golf & Country Club | Decorah | Iowa | United States of America | inactive |
| Onewhero Golf Club | Auckland | Auckland | New Zealand | inactive |
| Onga | Onga | Fukuoka |  Japan | inactive |
| Onga Onga Golf Club | Onga Onga | Hawke's Bay | New Zealand | inactive |
| ONGC /Ligripukhuri Golf Club | Nazira | Assam |  India | inactive |
| Ongerup Golf Club | Ongerup | Western Australia |  Australia | inactive |
| Onion Creek Golf Club | Austin | Texas | United States of America | inactive |
| Onishi | Onishi | Gunma | Japan | inactive |
| Onishi Terrace Golf Club | Nakagami | Okinawa | Japan | inactive |
| Onneley Golf Club | Cheshire | Staffordshire |  England | inactive |
| Onneyu Kokusai Country Club | Tokoro | Hokkaido | Japan | inactive |
| Ono Golf Club | Ono | Hyogo | Japan | inactive |
| Ono Grand Country Club | Ono | Hyogo | Japan | inactive |
| Ono Toyo Golf Club | Ono | Hyogo | Japan | inactive |
| Onomichi Country Club - Uneyama Course | Sera | Hiroshima | Japan | inactive |
| Onomichi Golf Club | Mihara | Hiroshima | Japan | inactive |
| Onomichi Uzushio Country Club | Onomichi | Hiroshima | Japan | inactive |
| Onondaga Golf and Country Club | Fayetteville | New York | United States of America | inactive |
| Onsjö Golfklubb | Vänersborg | Västra Götaland |  Sweden | inactive |
| Onsøy Golfklubb | Manstad | Østfold |  Norway | inactive |
| Ontake | Kani | Gifu | Japan | inactive |
| Ontario Country Club | Ontario | New York | United States of America | inactive |
| Onteora Club | Tannersville | New York | United States of America | inactive |
| Ontonagon Golf Course | Ontonagon | Michigan | United States of America | inactive |
| Onuma Kokusai Country Club | Kayabe | Hokkaido | Japan | inactive |
| Onuma Lake Golf Club | Kayabe | Hokkaido | Japan | inactive |
| Onward Mangilao Golf Club | Mangilao | Guam |  Guam | inactive |
| Onward Talofofo Golf Club | Talafofo | Guam | Guam | inactive |
| Onwentsia Club | Lake Forest | Illinois | United States of America | inactive |
| Onyx | Grand Blanc | Michigan | United States of America | inactive |
| Oodate Country Club | Oodate | Akita | Japan | inactive |
| Ooka Golf Club | Kinosaki | Hyogo | Japan | inactive |
| Oonodai Golf Club | Akita | Akita | Japan | inactive |
| Oosaki Golf Club | Shida | Miyagi | Japan | inactive |
| Oost-Zuid | Nunspeet | Gelderland |  Netherlands | inactive |
| Oost-Zuid | Groesbeek | Gelderland | Netherlands | inactive |
| Oostwoud-Westwoud | Benthuizen | Zuid-Holland | Netherlands | inactive |
| Ootacamund Gymkhana Golf Club | The Nilgiris | Tamil Nadu | India | inactive |
| Ootaka | Housu | Ishikawa | Japan | inactive |
| Ootawara Golf Club | Nasu | Tochigi | Japan | inactive |
| Ooyodogawa Golf Course | Miyazaki | Miyazaki | Japan | inactive |
| Opal Cove Resort Golf Course | Coffs Harbour | New South Wales | Australia | inactive |
| Open | Cotgrave | Nottinghamshire | England | inactive |
| Open | Dongguan | Guangdong |  China | inactive |
| Open | Fingal | Victoria | Australia | inactive |
| Open 9 | Myrtle Beach | South Carolina | United States of America | inactive |
| OPEN GOLF St. Johann Alpendorf | Sankt Johann im Pongau | Salzburg |  Austria | inactive |
| Open Golf Zandvoort | Zandvoort | Noord-Holland | Netherlands | inactive |