Similar:
* Satisfaction
* Fulfillment
* Gratification
* Pleasure
* Happiness
* Joy
* Peace
* Serenity
More nuanced:
* Well-being: A state of general happiness and satisfaction with life.
* Equanimity: A calm and composed state of mind, especially in difficult situations.
* At ease: Relaxed and comfortable.
* At peace: Free from worry or stress.
* Self-sufficiency: The ability to be happy and fulfilled without relying on external factors.
* Gratitude: A feeling of thankfulness for what one has.
* Acceptance: The ability to accept things as they are, without resistance or judgment.
The best synonym for "contentment" depends on the specific context in which you're using it.