Standby may refer to:
- Standby (air travel), a list in which passengers may request to be placed on to request an earlier or more convenient flight.
- Standby (theater), an actor or performer who will appear in a particular role if the regular performer is not present
- Sleep mode (in electronics), also known as standby-mode - a mode in which electronic appliances are turned off but under power and ready to activate on command
- Standby power energy consumed by an electronic device while it is turned off
- Standby, (or ACPI S3) an ACPI mode of a computer
- Standby, the term NASA uses in air-to-ground radio communications for expressing "please wait"