- Joint Allied Command: This body was created to coordinate the fighting forces of the Allied nations.
- Juggernaut: A term used to describe the relentless advance of the German army.
- Jim Crow laws: Racist laws that enforced racial segregation in the southern United States.
- June 28, 1914: The day that Archduke Franz Ferdinand of Austria was assassinated, triggering the outbreak of World War 1.
- Jutland: The site of a major naval battle between the British and German fleets.