How to say I just finished having breakfast in french?

There are a few ways to say "I just finished having breakfast" in French, depending on the level of formality you want:

Formal:

* Je viens de terminer mon petit déjeuner. (This is the most literal translation.)

Informal:

* J'ai fini de déjeuner. (This is a bit more natural and conversational.)

* J'ai fini de manger. (This is even more casual and means "I just finished eating.")

* Je viens de manger. (This is a very simple and common way to say "I just ate.")

You can also use the phrase "Je viens de prendre mon petit déjeuner" which means "I just had breakfast."

The best option for you will depend on the context and who you are talking to.