Royal Mahjong is a riichi mahjong (two-player variant) gambling game developed and released by Nichibutsu for arcades exclusively in Japan in 1981.
An early arcade mahjong game based on the game Janputer, Royal Mahjong is the progenitor of the "BET" variant of the genre, where the scoring and time systems are replaced with credit gambling.
Players in the game bet with their insert credits, and can earn additional credits by winning mahjong hands (with higher-value hands granting additional credits). Arcade operators can change the maximum amount of credits that can be bet at once (1, 5, 10, or 20) and the chance of the game providing a winnable hand (from 50% to 96%).
On each winning hand, players earn credits per yaku depending on their value:
- Yakuman - 500 per credit gambled
- Sanbaiman - 100 per credit gambled
- Baiman - 50 per credit gambled
- Haneman - 10 per credit gambled
- Mangan - 5 per credit gambled
- 3-han - 3 per credit gambled
- 2-han - 2 per credit gambled
- 1-han - 1 per credit gambled