Lockout-tagout (LOTO) or lock and tag is a safety procedure used in industry and research settings to ensure that dangerous machines are properly shut off and not able to be started up again prior to the completion of maintenance or repair work.

A lockout uses a lock to hold an energy isolation device in a safe position and prevents the energization of the machine or equipment. Tagout is when a tag is placed on a piece of equipment to indicate that the equipment being controlled may not be operated until the tagout device is removed.