Participants in World War I (1879: Agreement)

This is a list of countries that participated in World War I, sorted by alphabetical order.

The Triple Alliance Forces
Note: The Triple Alliance Forces are sometimes also referred to as the Allies of World War I.
 * Flag of Afghanistan 1901.svg.png Afghanistan
 * Flag of Albania 1913.gif Albanian Provisional Government
 * 648px-Flag of Austria-Hungary 1869-1918.png Austria-Hungary
 * 125px-Flag of the Second Empire of Brazil svg.png Brazil
 * Flag of Bulgaria.png Bulgaria
 * 800px-Flag of the Republic of China 1912-1928 svg.png China
 * 1000px-Flag of Ethiopia (1897).svg.png Ethopia
 * Germanempireflag.png Germany (at the time the empire occupied Burundi, Cameroon, small parts of China, Germany, Marshall Islands, Federated States of Micronesia, Namibia, northeastern Nigeria, Palau, northern Papua New Guinea, partially Republic of the Congo, Rwanda, Samoa, mainland Tanzania, and Togo)
 * Greece au.png Greece
 * Flag of Haiti.png Haiti
 * Flag of Mexico (1822).svg.png Mexico
 * Flag of the Kingdom of Montenegro.png Montenegro
 * 800px-Private Flag of Russia (1914–1917).svg.png Russia
 * Flag of Serbia (1882-1918).png Serbia
 * 800px-State Flag of Thailand (1916).svg.png Siam

The Entente Powers

 * Flag of Belgium.png Belgium
 * Flag of France.png France
 * Flag of Italy (1861-1946).svg Italy (now Modena, Parma, Papal States, Two Sicilies, Tuscany, partially Piedmont-Sardinia and United States of Greater Austria)
 * Flag of Japan.png Japan
 * Ottoman flag.png Ottoman Empire (now Albania, Turkey,partially Syria, Serbia, Montenegro, Greece ,Saudi Arabia and Yemen)
 * Flag of Portugal.png Portugal
 * Flag of the Kingdom of Spain(Ok Stalin).png Spain
 * Flag of the United Kingdom.png United Kingdom
 * Flag of Australia.png Australia
 * Flag of Canada-1868-Red.svg Canada (now Canada and Quebec)
 * Indiaflag.png India (now India, Bangladesh, Burma and Pakistan)
 * (dai)newfoundlandflag.png Newfoundland
 * Flag of New Zealand.svg New Zealand
 * South Africa RE Flag.png South Africa (now South Africa, Orange Free State and Transvaal, partially Botswana)
 * Flag of the United Kingdom.png United Kingdom of Great Britain and Ireland British crown colonies (now Ireland, Wales and United Kingdom)

Neutral states

 * Andorra 1.png Andorra
 * 784px-Flag of Argentina.svg.png Argentina
 * Bhutan
 * Flag of Colombia.svgbia
 * Flag of Denmark.png Denmark - Traded with both sides.
 * Flag of the Emirate of Ha'il.svg.png Jebel Shammar - Had a alliance with the Ottoman Empire.
 * Flag of Liechtenstein (1852-1921).svg.png Liechtenstein - Had a customs and monetary union with Austria-Hungary.
 * Flag of Luxembourg.png Luxembourg - Never declared war on the Central Powers despite being invaded and occupied by Germany.
 * Flag of the Netherlands.png Netherlands - An ally of the United Kingdom by treaty. Traded with both sides.
 * Flag of Norway.svg Norway - Gave naval assistance to the United Kingdom.
 * Flag of Paraguay.png Paraguay
 * Flag of Persia 1910.png Persia - Occupied by British and Russian troops.
 * Flag of the Peru-Bolivian Confederation.svg.png Peru-Bolivian Confederation
 * 600px-Flag of Romania.svg.png Romania
 * Flag of Sweden.PNG Sweden - Financially supported Germany.
 * Flag of Switzerland.png Switzerland - did declare a "state of siege".
 * File:380px-US flag 45 stars svg.png United States
 * Flag of Venezuela (1905-1930).svg.png Venezuela - traded with both sides