在 HTML 中，国家代码可用作 lang 属性中语言代码的补充。
语言代码的前两个字符定义了网页的语言（请参阅语言代码参考）。
最后两个字符定义国家。
以下示例将英语指定为语言，将美国指定为国家：
<html lang="en-US">
...
</html>
| 国家/地区 | ISO 代码 |
|---|---|
| AFGHANISTAN | AF |
| ALBANIA | AL |
| ALGERIA | DZ |
| AMERICAN SAMOA | AS |
| ANDORRA | AD |
| ANGOLA | AO |
| ANTARCTICA | AQ |
| ANTIGUA AND BARBUDA | AG |
| ARGENTINA | AR |
| ARMENIA | AM |
| ARUBA | AW |
| AUSTRALIA | AU |
| AUSTRIA | AT |
| AZERBAIJAN | AZ |
| BAHAMAS | BS |
| BAHRAIN | BH |
| BANGLADESH | BD |
| BARBADOS | BB |
| BELARUS | BY |
| BELGIUM | BE |
| BELIZE | BZ |
| BENIN | BJ |
| BERMUDA | BM |
| BHUTAN | BT |
| BOLIVIA | BO |
| BOSNIA AND HERZEGOVINA | BA |
| BOTSWANA | BW |
| BOUVET ISLAND | BV |
| BRAZIL | BR |
| BRITISH INDIAN OCEAN TERRITORY | IO |
| BRUNEI DARUSSALAM | BN |
| BULGARIA | BG |
| BURKINA FASO | BF |
| BURUNDI | BI |
| CAMBODIA | KH |
| CAMEROON | CM |
| CANADA | CA |
| CAPE VERDE | CV |
| CAYMAN ISLANDS | KY |
| CENTRAL AFRICAN REPUBLIC | CF |
| CHAD | TD |
| CHILE | CL |
| CHINA | CN |
| CHRISTMAS ISLAND | CX |
| COCOS (KEELING) ISLANDS | CC |
| COLOMBIA | CO |
| COMOROS | KM |
| CONGO | CG |
| CONGO, THE DEMOCRATIC REPUBLIC OF THE | CD |
| COOK ISLANDS | CK |
| COSTA RICA | CR |
| CÔTE D'IVOIRE | CI |
| CROATIA | HR |
| CUBA | CU |
| CYPRUS | CY |
| CZECH REPUBLIC | CZ |
| DENMARK | DK |
| DJIBOUTI | DJ |
| DOMINICA | DM |
| DOMINICAN REPUBLIC | DO |
| ECUADOR | EC |
| EGYPT | EG |
| EL SALVADOR | SV |
| EQUATORIAL GUINEA | GQ |
| ERITREA | ER |
| ESTONIA | EE |
| ETHIOPIA | ET |
| FALKLAND ISLANDS (MALVINAS) | FK |
| FAROE ISLANDS | FO |
| FIJI | FJ |
| FINLAND | FI |
| FRANCE | FR |
| FRENCH GUIANA | GF |
| FRENCH POLYNESIA | PF |
| FRENCH SOUTHERN TERRITORIES | TF |
| GABON | GA |
| GAMBIA | GM |
| GEORGIA | GE |
| GERMANY | DE |
| GHANA | GH |
| GIBRALTAR | GI |
| GREECE | GR |
| GREENLAND | GL |
| GRENADA | GD |
| GUADELOUPE | GP |
| GUAM | GU |
| GUATEMALA | GT |
| GUINEA | GN |
| GUINEA-BISSAU | GW |
| GUYANA | GY |
| HAITI | HT |
| HEARD ISLAND AND MCDONALD ISLANDS | HM |
| HONDURAS | HN |
| HONG KONG | HK |
| HUNGARY | HU |
| ICELAND | IS |
| INDIA | IN |
| INDONESIA | ID |
| IRAN, ISLAMIC REPUBLIC OF | IR |
| IRAQ | IQ |
| IRELAND | IE |
| ISRAEL | IL |
| ITALY | IT |
| JAMAICA | JM |
| JAPAN | JP |
| JORDAN | JO |
| KAZAKHSTAN | KZ |
| KENYA | KE |
| KIRIBATI | KI |
| KOREA, DEMOCRATIC PEOPLE'S REPUBLIC OF | KP |
| KUWAIT | KW |
| KYRGYZSTAN | KG |
| LAO PEOPLE'S DEMOCRATIC REPUBLIC | LA |
| LATVIA | LV |
| LEBANON | LB |
| LESOTHO | LS |
| LIBERIA | LR |
| LIBYA, STATE OF | LY |
| LITHUANIA | LT |
| LUXEMBOURG | LU |
| MACAO | MO |
| MACEDONIA, THE FORMER YUGOSLAV REPUBLIC OF | MK |
| MADAGASCAR | MG |
| MALAWI | MW |
| MALAYSIA | MY |
| MALDIVES | MV |
| MALI | ML |
| MALTA | MT |
| MARSHALL ISLANDS | MH |
| MARTINIQUE | MQ |
| MAURITANIA | MR |
| MAURITIUS | MU |
| MAYOTTE | YT |
| MEXICO | MX |
| MICRONESIA, FEDERATED STATES OF | FM |
| MOLDOVA, REPUBLIC OF | MD |
| MONACO | MC |
| MONTENEGRO | ME |
| MONTSERRAT | MS |
| MOROCCO | MA |
| MOZAMBIQUE | MZ |
| MYANMAR | MM |
| NAMIBIA | NA |
| NAURU | NR |
| NEPAL, FEDERAL DEMOCRATIC REPUBLIC OF | NP |
| NETHERLANDS | NL |
| NETHERLANDS ANTILLES | AN |
| NEW CALEDONIA | NC |
| NEW ZEALAND | NZ |
| NICARAGUA | NI |
| NIGER | NE |
| NIGERIA | NG |
| NIUE | NU |
| NORFOLK ISLAND | NF |
| NORTHERN MARIANA ISLANDS | MP |
| NORWAY | NO |
| OMAN | OM |
| PAKISTAN | PK |
| PALAU | PW |
| PALESTINE, STATE OF | PS |
| PANAMA | PA |
| PAPUA NEW GUINEA | PG |
| PARAGUAY | PY |
| PERU | PE |
| PHILIPPINES | PH |
| PITCAIRN | PN |
| POLAND | PL |
| PORTUGAL | PT |
| PUERTO RICO | PR |
| QATAR | QA |
| RÉUNION | RE |
| ROMANIA | RO |
| RUSSIAN FEDERATION | RU |
| RWANDA | RW |
| SAINT HELENA | SH |
| SAINT KITTS AND NEVIS | KN |
| SAINT LUCIA | LC |
| SAINT PIERRE AND MIQUELON | PM |
| SAINT VINCENT AND THE GRENADINES | VC |
| SAMOA | WS |
| SAN MARINO | SM |
| SAO TOME AND PRINCIPE | ST |
| SAUDI ARABIA | SA |
| SENEGAL | SN |
| SERBIA | RS |
| SEYCHELLES | SC |
| SIERRA LEONE | SL |
| SINGAPORE | SG |
| SLOVAKIA | SK |
| SLOVENIA | SI |
| SOLOMON ISLANDS | SB |
| SOMALIA | SO |
| SOUTH AFRICA | ZA |
| SOUTH GEORGIA AND THE SOUTH SANDWICH ISLANDS | GS |
| SOUTH SUDAN | SS |
| SPAIN | ES |
| SRI LANKA | LK |
| SUDAN | SD |
| SURINAME | SR |
| SVALBARD AND JAN MAYEN | SJ |
| SWAZILAND | SZ |
| SWEDEN | SE |
| SWITZERLAND | CH |
| SYRIAN ARAB REPUBLIC | SY |
| TAIWAN | TW |
| TAJIKISTAN | TJ |
| TANZANIA, UNITED REPUBLIC OF | TZ |
| THAILAND | TH |
| TIMOR-LESTE | TL |
| TOGO | TG |
| TOKELAU | TK |
| TONGA | TO |
| TRINIDAD AND TOBAGO | TT |
| TUNISIA | TN |
| TURKEY | TR |
| TURKMENISTAN | TM |
| TURKS AND CAICOS ISLANDS | TC |
| TUVALU | TV |
| UGANDA | UG |
| UKRAINE | UA |
| UNITED ARAB EMIRATES | AE |
| UNITED KINGDOM | GB |
| UNITED STATES | US |
| UNITED STATES MINOR OUTLYING ISLANDS | UM |
| URUGUAY | UY |
| UZBEKISTAN | UZ |
| VANUATU | VU |
| VENEZUELA | VE |
| VIET NAM | VN |
| VIRGIN ISLANDS, BRITISH | VG |
| VIRGIN ISLANDS, U.S. | VI |
| WALLIS AND FUTUNA | WF |
| WESTERN SAHARA | EH |
| YEMEN | YE |
| ZAMBIA | ZM |
| ZIMBABWE | ZW |