This is the most common question new learners ask, and the answer depends a lot on how much time you study and what "fluent" means to you.

The general consensus from experienced learners is: with consistent daily study (1 hour per day), you can have basic conversational fluency in about 1-2 years. Reaching advanced fluency takes 3-5 years.

The key is consistency - 15 minutes every day works better than 3 hours once a week. Check the link above for real experiences from people who've gotten there.