Formal:
* Gavan: This is the most common and straightforward way to write Gavin in French.
* Gavin: You can also use the English spelling, but it will be pronounced with a French accent.
Informal:
* Gaëtan: This name is similar in sound and meaning to Gavin, and it's a common French name.
* Gaël: Similar to Gaëtan, but slightly less common.
Ultimately, the best way to say "Gavin" in French depends on the context and your preference.