Olga Zimina vs Kateryna Alexandrovna Lahno
European Club Cup (Women) Rhodes GRE round 1.1 2013.10.20
Réti Opening 0-1

Oliver Barbosa vs Krishnan Sasikiran
10th Asian Individual Championship Mashhad IRI round 1.2 2011.05.02
King’s Indian Defense: Sämisch Variation 1/2-1/2

Oliver Jackson vs Michael Adams
Sheffield Sheffield 1991.??.??
King’s Gambit Accepted 0-1

Olof Sterner vs Reinhart Fuchs
Dresden it Dresden GDR round 3 1956.02.??
Ruy Lopez: Morphy Defense, Anderssen Variation 1/2-1/2

Orazly Annageldyev vs Pia Cramling
Manila Olympiad Manila PHI round 5 1992.06.12
Benko Gambit 0-1

Ortvin Sarapu vs Ylvi Pustina
Siegen ol (Men) qual-F Siegen FRG round 8 1970.09.12
Sicilian Defense: Taimanov Variation, Bastrikov Variation 1/2-1/2

Oscar Chajes vs William Widmeyer
10th Western Championship Excelsior, MN USA round 15 1909.08.24
Italian Game: Evans Gambit 1-0

Oscar Gelbfuhs vs Henry Edward Bird
Vienna Vienna AUH round 1.1 1873.07.21
Ruy Lopez: Bird Variation 0-1

Oswald Bindrich vs Jorge Flores Chico
Gibraltar La Caleta GIB round 9 2010.02.03
Sicilian Defense: Dragon Variation, Yugoslav Attack, Belezky Line 1-0

Otto Loewenborg vs M Hajn
Mlada Boleslav-B Mlada Boleslav AUH 1913.??.??
Caro-Kann Defense: Classical Variation 1-0