List of sovereign states in the 1900s

A

• Aceh – Sultanate of Aceh (to 1903)
  Capital: Kutaraja

• Acre – Republic of Acre (from January 15 to May 13, 1903 and from August 31, 1903 to February 25, 1904)
  Capital: Cidade do Acre

• Andorra – Principality of Andorra
  Capital: Andorra la Vella

•  Argentina – Argentine Republic
• Aro – Aro Confederacy (to January 1902)
• →  Australia – Commonwealth of Australia
•  Austria-Hungary – Austro-Hungarian Empire

B

•  Beihan – Emirate of Beihan (to January 1904)
•  Belgium – Kingdom of Belgium
•  Bhutan
  • Bhutan (to December 17, 1907)
  • Kingdom of Bhutan (from December 17, 1907)
•  Bolivia – Republic of Bolivia
• Brazil – Republic of the United States of Brazil
•  Bulgaria – Kingdom of Bulgaria (from October 5, 1908)

C

•  Canada – Dominion of Canada
• Champasak – Kingdom of Champasak (to November 22, 1904)
•  Chile – Republic of Chile
•  China – Great Qing Empire
•  Colombia – Republic of Colombia
•  Congo – Congo Free State (to November 15, 1908)
•  Costa Rica – Republic of Costa Rica
•  Crete – Cretan State (from October 6, 1908)
•  Cuba – Republic of Cuba (from May 20, 1902)

D

•  Denmark – Kingdom of Denmark
•  Dhala – Emirate of Dhala (to 1904)
•  Dominican Republic – Dominican Republic

E

• Ecuador – Republic of Ecuador
• El Salvador – Republic of El Salvador
•  Ethiopia – Ethiopian Empire

F

•  France – French Republic

G

•  Germany – German Realm
•  Greece – Kingdom of Greece
•  Guatemala – Republic of Guatemala

H

• Ha'il – Emirate of Ha'il
•  Haiti – Republic of Haiti
• Honduras – Republic of Honduras

I

•  Italy – Kingdom of Italy

J

•  Japan – Empire of Japan

K

• Kano – Emirate of Kano (to February 3, 1903)
•  Korea – Greater Korean Empire (to November 17, 1905)
• Kruševo Republic – Kruševo Republic (from August 3 to August 13, 1903)

L

•  Liberia – Republic of Liberia
•  Liechtenstein – Principality of Liechtenstein
•  Luxembourg – Grand Duchy of Luxembourg

M

•  Mexico – United Mexican States
•  Monaco – Principality of Monaco
•  Montenegro – Principality of Montenegro
•  Morocco – Sultanate of Morocco

N

• Nejd – Emirate of Nejd (from January 15, 1902)
• Nepal – Kingdom of Nepal
•  Netherlands – Kingdom of the Netherlands
•  Newfoundland – Dominion of Newfoundland (from September 26, 1907)
• New Zealand – Dominion of New Zealand (from September 26, 1907)
• Nicaragua – Republic of Nicaragua
•  Norway – Kingdom of Norway (in personal union with Sweden until June 7, 1905)

O

•  Orange Free State – Republic of Orange Free State (to May 31, 1902)
•  Ottoman Empire – Sublime Ottoman State
•  Ouaddai – Ouaddai Empire

P

• →  Panama – Republic of Panama (from November 3)
•  Paraguay – Republic of Paraguay
• → → Persia – Persian Empire
•  Peru – Peruvian Republic
• Portugal – Kingdom of Portugal

R

•  Romania – Kingdom of Romania
•  Russia – Russian Empire

S

•  San Marino – Most Serene Republic of San Marino
•  Serbia – Kingdom of Serbia
•  Siam – Kingdom of Siam
• Sokoto – Sokoto Caliphate (to July 7)

South African Republic Transvaal

• Spain – Kingdom of Spain
• Swaziland – Kingdom of Swaziland (to 1902)
• →  Sweden – Kingdom of Sweden {{small|(in personal union with Norway until June 7, 1905)^{[lower-alpha 1]}
•   Switzerland – Swiss Confederation

T

• Tagalog Republic (from 1902 to July 14, 1906)
• Tavolara – Kingdom of Tavolara
• Tonga – Kingdom of Tonga (1900–70) from May 18, 1900
•  Transvaal – South African Republic (until May 31, 1902)

U

•  United Kingdom – United Kingdom of Great Britain and Ireland
• →  United States – United States of America
•  Upper Aulaqi Sultanate (to 1904)
•  Upper Aulaqi Sheikhdom (to 1903)
•  Upper Yafa – Sultanate of Upper Yafa (to 1903)
•  Uruguay – Eastern Republic of Uruguay

V

• →  Venezuela – United States of Venezuela

W

•  Wahidi Balhaf – Wahidi Sultanate of Balhaf (to 1905)
•  Wahidi Haban – Wahidi Sultanate of Haban (to 1905)