ClubLocationLeagueTierFounded
Odorheiu Secuiesc—Liga III - Seria VI—1922Olimpia Arad—Dissolved 19??—1920Olimpia Gherla——Olimpia Salonta—Liga IV - Bihor—1911Olimpia Satu Mare—Liga III—1921Olimpic Cetate Râșnov—Liga III—1930Olt Scorniceşti——Olt Scornicești—Liga IV - Olt—1972Olt Slatina—Dissolved 2016—2006Oltul Sfântu Gheorghe——Onești——Otopeni—Dissolved 2013—2001Ozana Târgu Neamț—Dissolved 2020—1974Oțelul Galați II——