Valor and valour both mean great courage, especially in battle. Valour is the British spelling and valor is the American one, so a British citation would praise a soldier's valour, while a US citation would praise their valor.
The core difference
The meaning is identical; only the spelling varies, with valour used in British English and valor in American English.
- valour — British spelling, meaning great courage in danger: He was awarded a medal for valour after pulling two soldiers from the wreckage.
- valor — American spelling of the same word, used in place of valour in US English.
How to tell them apart
Valour traces back through Anglo-Norman valour to the Latin valor, related to valere, meaning to be strong. That Latin root is also where the American spelling valor comes from directly, which is part of why American English dropped the extra u.
The word turns up most often in military honours and formal citations, where getting the house spelling right matters: British and Commonwealth awards use valour, while American ones use valor.