Nouns ending in -tion are feminine.
The suffix forms abstract nouns of action or state.
Is félicitation masculine or feminine?
lafélicitation
The rule behind it
99.8% of -tion nouns are feminine
In context
Il m'a envoyé un télégramme de félicitations.
He telegraphed me his congratulations.
Félicitations aux mains qui ont rendu cela possible.
My compliments to the hands that made this possible.
Avec cette performance, tu t'es surpassé. Félicitations !
With that performance, you have surpassed yourself. Congratulations!