Nouns ending in -tion are feminine.
The suffix forms abstract nouns of action or state.
Is organisation masculine or feminine?
l'organisation
The rule behind it
99.8% of -tion nouns are feminine
In context
Cette organisation promeut l'alphabétisation des zones rurales.
This organisation promotes literacy in rural areas.
Cette organisation est corrompue jusqu'à l'os.
That organization is corrupt to its core.
Les Nations Unies sont une organisation internationale.
The United Nations is an international organization.