CountryCallingCodes.com and NationsOnline.org list internationally recognized country codes issued by the International Standards Organization. CountryCallingCodes.com lists the Alpha-2 and Alpha-3 code for each country, while NationsOnline.org lists the Alpha-2, Alpha-3 and UN M49 code.
To find an international country code at CountryCallingCodes.com, click on the ISO Country Codes tab on the vertical navigation bar on the left of the main page, and then click on the name of the continent where the country is located to bring up a list of all countries on that continent, along with their respective Alpha-2 and Alpha-3 codes.
At NationsOnline.org, click on the One World -- Nations Online link near the top of the main page, then select the Int'l Codes tab at the top right of the next page. Select the International Country Codes link from the descriptions of country code types, and then on the following page click on Country Codes List in bold blue near the right center of the page to bring up a list of all countries, along with their Alpha-2, Alpha-3 and UN M49 numerical codes.
ISO country codes are designators for countries and certain dependencies and other territories. There are three types of codes: an Alpha-2 code consisting of a two-letter combination such, as .us for the United States; an Alpha-3 code consisting of a three-letter combination, such as CAN for Canada; and an M49 code used by the United Nations, such as 702 for Singapore.