Formal:
* I speak French. (This is the most common and straightforward way to say it.)
* I am fluent in French. (This emphasizes your level of proficiency.)
* I have a good command of French. (This implies a high level of understanding and speaking ability.)
Informal:
* I can speak French. (This is a simpler and more casual way to say it.)
* I know French. (This is even more casual and may not imply fluency.)
Other options:
* I'm a French speaker. (This is a more specific way to describe yourself.)
* I'm learning French. (This indicates that you're still studying the language.)
You can choose the best option depending on who you're talking to and what you want to convey.