Starts with the letter 'O'
- Oblong Chess 44. Based on the original oriental variant "Oblong Chess", a 16X4 Shataranj variant, but reducing the number of lines. Author: Jeff Rients. Inventor: Erez Schatz.
- Octopus Chess. Featuring the Sorcerer Snake, the Ninja Pawn, the Wazir Knight, the Ferz Knight and the Octopus. By Charles Daniel.
- Odin's Rune Chess. With pieces that were inspired by rune images and meanings.... By Gary K. Gifford.
- Omega Chess. This preset for Omega Chess enforces the rules and spots check, checkmate, and stalemate. Author: Fergus Duniho.
- Omega Transplant. The Champion and Wizard from Omega Chess are transplanted to the board system and rules used for Birds and Ninjas. By Charles Daniel.
- Opulent Chess. Play this derivative of Grand Chess with additional jumping pieces (Lion and Wizard). By Greg Strong.
- Opulent Lemurian Shatranj. Joe Joyce's Shaman and Hero pieces are on a large board. By David Paulowich.
- Orphic Chess. Before the King is dropped the pieces can only capture. A very tactical and fast variant. By M Winther.
- Orphic Chess (with Elks). Before the King is dropped the pieces can only capture. A very tactical and fast variant, with Elks. By M Winther.
- Outback Chess. Play this game with new pieces on plus-shaped board. Winner of the 84-square contest! Author: Tony Quintanilla and Timothy R. Newton. Inventor: Timothy R. Newton.
- OverKnight Chess. Pawns are replaced by Knights, which promote. Author: Tony Quintanilla
- Oxybeles Chess. The Oxybeles can sling a piece to the farthest square in the movement direction (+zrf). By M Winther.
|12 'Play by mail item' entries listed||6 'Large board' entries listed|
|1 'Unorthodox shaped board' entry listed|
Total items listed: 12