Starts with the letter 'O'
- Octa-Ashtapada. 8x8x8 variant with powerful armies and the potential for multiple royal pieces per side.
- Octahedral Chess. 3d-board in octahedral form. (x9, Cells: 340)
- OctHex 146. Arranging the geometry of Tetrahedral Chess into an octahedron. (Cells: 146)
- Odalisque Chess. Magnetic rotating three dimensional chess variant. (1x4x16, Cells: 64)
- Óskar's 3dchess. Missing description (8x8x5, Cells: 320)
- Óskar's 3dchess version 2. Missing description (8x8x5, Cells: 320)
|5 'Game' entries listed||1 'Zillions of Games file' entry listed|
|6 'Three dimensional' entries listed||1 'Large board' entry listed|
|1 'Unorthodox shaped board' entry listed||1 'Board with hexagonal shaped cells' entry listed|
Total items listed: 6