- Belgium
- Brazil
- British Empire
- China
- Cuba
- Czechoslovakia
- France
- Greece
- Guatemala
- Haiti
- Hejaz
- Honduras
- Italy (joined in 1915)
- Japan
- Liberia
- Montenegro
- Nicaragua
- Panama
- Portugal
- Romania (joined in 1916)
- Russia (until November 1917)
- San Marino
- Serbia
- Siam (Thailand)
- United States (joined in 1917)
- Uruguay
Allied Powers of World War II:
- Australia
- Belgium
- Brazil
- Canada
- China
- Cuba
- Czechoslovakia
- Denmark
- Ethiopia
- France
- Greece
- India
- Luxembourg
- Mexico
- Netherlands
- New Zealand
- Nicaragua
- Norway
- Panama
- Philippines (Commonwealth)
- Poland
- South Africa
- Soviet Union
- United Kingdom
- United States
- Yugoslavia