Rayo is an abbreviation of Rayo Vallecano, a Spanish professional football club.
Rayo or rayo may also refer to:
- Rayo (album), by J Balvin (2024)
- Rayo (name)
- Rayo's number, a large number named after Agustín Rayo
- Rayo(n), the smallest k greater than all numbers Rayo-nameable in at most n symbols