YAI may be an abbreviation for:
- Youth Action International, a non-profit organization
Yai may refer to:
- Yai River, Thailand
- a human given name, as in the case of Yai Nilwong, a Thai footballer
YAI or yai may also be an official code:
- IATA airport code YAI: General Bernardo O'Higgins Airport, Chillán, Chile
- ISO 639-3 language code yai: Yaghnobi language, a living, East Iranian language