General synonyms:
* Bravery
* Boldness
* Daring
* Gallantry
* Mettle
* Nerve
* Spirit
* Valour
More specific synonyms:
* Fortitude: Strength of mind that enables one to endure pain or hardship.
* Intrepidity: Fearlessness, especially in the face of danger.
* Audacity: Daring or boldness.
* Grit: Determination and resilience.
* Resilience: The ability to recover quickly from difficulties.
* Tenacity: Persistence and determination.
* Stoicism: Calm acceptance of what cannot be changed.
The best synonym for "courage" will depend on the specific context of your writing.