A dog tag is the informal name for the identification tags worn by military personnel, named such as it bears resemblance to actual dog tags. The tag is primarily used for the identification of dead and wounded and essential basic medical information for the treatment of the latter, such as blood type and history of inoculations, along with providing religious preference. Dog tags are usually fabricated from a corrosion-resistant metal or alloy such as aluminum, monel or stainless-steel, although, during wartime, they have been made from whatever metals were available. In the US military, if the member has a medical condition that requires special attention, an additional, red tag with the pertinent information is issued and worn with the dog tags.

In the US Military, wearing of the tag is required at all times by soldiers in the field. It may contain two copies of the information and be designed to break easily into two pieces. This allows half the tag to be collected for notification while the other half remains with the body when battle conditions do not allow the casualty to be immediately recovered. Alternatively, in the US Military, two identical tags are issued. One is worn on a long chain around the neck; the second on a much smaller chain attached to the first chain. In the event the wearer is killed, the second tag is collected, and the first remains with the body. Alternatively, some units allow or require each member to wear one laced into their boot in lieu of the second around the neck.