Cai can refer to:
- Cai (surname), a common Chinese surname
- Cai (state), a state in ancient China
- Caí River, Rio Grande do Sul, Brazil
- Cái River, Vietnam
- Sir Kay, a character in Arthurian legend, spelt Cai in Welsh
- A green, leafy Chinese vegetable (Cant. "choy")
CAI is a three-letter acronym that can refer to:
Read more about Cai: Common Noun Phrases, Proper Names