• Aftermath of World War I by country (16 C)
• Military operations of World War I by country (15 C)
• Entry into World War I by country (1 C, 9 P)
• World War I films by country (18 C)
• World War I memorials by country (23 C)
• World War I military equipment by country (12 C)
• People of World War I by nationality (50 C)
• Military units and formations of World War I by country (20 C)

+

• Allies of World War I (4 C, 16 P)

A

• Albania in World War I (3 C, 13 P)
• Argentina in World War I (5 P)
• Australia in World War I (3 C, 18 P)
• Austria-Hungary in World War I (14 C, 56 P, 12 F)

B

• Belgian Congo in World War I (2 C, 9 P)
• Belgium in World War I (5 C, 20 P, 6 F)
• Bermuda in World War I (1 C, 5 P)
• Brazil in World War I (2 C, 3 P, 1 F)
• British Empire in World War I (14 C, 39 P)
• Bulgaria in World War I (7 C, 24 P)

C

• Canada in World War I (7 C, 37 P)
• China in World War I (2 C, 10 P)

D

• Denmark in World War I (3 P)

E

• Egypt in World War I (1 C, 21 P)

F

• France in World War I (9 C, 31 P, 31 F)

G

• German Empire in World War I (15 C, 103 P, 27 F)
• Greece in World War I (5 C, 24 P)

I

• India in World War I (5 C, 15 P)
• Iran in World War I (6 P)
• Italy in World War I (7 C, 28 P)

J

• Japan in World War I (5 C, 12 P)

L

• Libya in World War I (1 P)
• Liechtenstein in World War I (2 C, 2 P)
• Luxembourg in World War I (1 C, 9 P)

M

• Malta in World War I (1 C, 1 P)
• Montenegro in World War I (2 C, 6 P)

N

• Nepal in World War I (1 C, 1 P)
• New Zealand in World War I (5 C, 31 P)
• Nigeria in World War I (1 C, 4 P)
• Norway in World War I (3 P)

O

• Ottoman Empire in World War I (14 C, 59 P)

P

• Papua New Guinea in World War I (1 C)
• Poland in World War I (8 C, 31 P)
• Portugal in World War I (3 C, 8 P)

R

• Rhodesia in World War I (3 C, 3 P)
• Romania in World War I (10 C, 43 P)
• Russian Empire in World War I (11 C, 40 P)

S

• Serbia in World War I (8 C, 44 P)
• Soviet Russia in World War I (17 P)
• Switzerland in World War I (4 P)

U

• Ukraine in World War I (3 C, 26 P)
• United Kingdom in World War I (11 C, 122 P)
• United States in World War I (8 C, 30 P, 29 F)
• Uruguay in World War I (2 P)

C

• Cuba during World War I

E

• Ethiopia in World War I

H

• Haiti during World War I
• Honduras in World War I
• Hong Kong during World War I
• Hungary in World War I

L

• List of last surviving World War I veterans
• Liberia in World War I

M

• Mexico in World War I

N

• Nepal during World War I
• Netherlands in World War I
• Niue in World War I

S

• Siam in World War I
• Spain during World War I
• Sweden during World War I

T

• Triple Alliance (1882)
• Triple Entente

V

• Vietnam during World War I
• Venezuela during World War I