Olafs Krumins vs Alfreds Akmentins
Latvian championship Riga LAT 1948.??.??
Barnes Defense 0-1

Olamide Patrick Ajibowo vs Tito Kahn
Chess Olympiad Khanty-Mansiysk RUS round 10 2010.10.01
Russian Game 1-0

Olav Sepp vs Yuriy Kryvoruchko
27th Cappelle-la-Grande Cappelle la Grande FRA round 3.11 2011.02.28
Colle System: Rhamphorhynchus Variation 0-1

Oldrich Duras vs Oscar Chajes
Quadrangular Masters New York, NY USA round 3 1913.09.06
Queen’s Gambit Declined: Alekhine Variation 1-0

Oleg Badmatsyrenov vs Aleksandr Rakhmanov
Russian Championship Higher League Ulan Ude RUS round 4 2009.09.05
Sicilian Defense: Nimzowitsch Variation 0-1

Oleg Evstratov vs Baira Kovanova
Chigorin mem open St. Petersburg RUS round 9 2001.10.03
Blackmar-Diemer Gambit: Netherlands Variation 1/2-1/2

Olga L Latypova vs Keith Arkell
British Championship Hull ENG round 2 2021.10.03
Czech Defense 0-1

Olof Sterner vs Victor Ciocaltea
Dresden it Dresden GDR round 1 1956.02.26
Sicilian Defense: Sozin Attack, Fischer Variation 0-1

Orestes Rodriguez Vargas vs Alexey Dreev
ESP-URS Logrono ESP 1991.11.??
Slav Defense 0-1

Orestes Rodriguez Vargas vs Haji Ardiansyah
Chess Olympiad Final-B Skopje YUG round 1 1972.09.27
Sicilian Defense: Najdorf Variation, Main Line 1/2-1/2