APO, or Army Post Office, is an address where civilians can send service members from the United States Army and United States Air Force mail; service members can send or receive mail from this same location. APO mail is domestic or international mail that includes a United States military return or delivery address that is in the possession of the Department of Defense. To find an APO address, you need a ZIP code for the specific APO.

Visit APO Box (see Resources).

Type the nine-digit APO ZIP code into the "Enter ZIP" field and then click "Submit."

Write down the country, city and installation. The installation is the military base where the service member is stationed. This is the APO address of the service member and you can send mail to this address.