In contract bridge, relay is a general term for conventional bidding of (usually) the cheapest available bid. The relay bid normally has no descriptive meaning, i.e. its primary purpose is to give partner room to describe his hand instead. Thus, a relay bid is not a convention per se, but a part of many other conventions.

The rationale for introducing relay bids emerged from the idea that it is not always cost-effective (i.e. the best use of bidding space) for both partners to describe their hands. Instead, only one partner can make the cheapest bids available (relays) while the other describes his hand.

Relay bidding systems are for the most part based on relay bids: in most sequences (especially forcing ones), one partner just relays while the other describes his hand in a highly codified manner. While relay systems offer a higher level of exchanged information than natural systems, they also have the drawbacks that they are complicated to memorize and often exclude the players' judgment, particular in regard to honor location, which can be crucial on occasion.

Relay bids are a part of several conventions:

• Lebensohl (3♣ relay by 1NT opener, waiting for the partner to declare his hand)
• Cappelletti (2♦ relay over partner's 2♣ overcall, meaning "pass or correct")