A relay is an electric switch operated by a signal in one circuit to control another circuit.
Relay may also refer to:
- Relay (satellite)
- Broadcast relay station, a transmitter which repeats or transponds the signal of another
- Microwave radio relay
- Relay channel, in information theory, a communications probability modeling system
- Telecommunications Relay Service, a telephone accessibility service for the deaf
- Repeater, an electronic device that receives and retransmits a signal
- Relay (shop), a France-based chain of convenience stores
- Relay (company), a peer-to-peer political texting platform
- "Relay" (song), 1972, by The Who
- Relay bid, in contract bridge
- Relay race, completed in parts by several participants of a team
- Relay neuron, in anatomy
- Relay box, a piece of postal infrastructure.