Nouns ending in -tion are feminine.
The suffix forms abstract nouns of action or state.
Is inspiration masculine or feminine?
l'inspiration
The rule behind it
99.8% of -tion nouns are feminine
In context
Quelle est votre plus grande source d'inspiration ?
What is your greatest source of inspiration?
Quelle est ta plus grande source d'inspiration ?
What is your greatest source of inspiration?
Il se dressa et prit une longue inspiration.
He stood up and took a deep breath.