UPDATED 2024 - I am asked all the time for help with itineraries to France. If you've been before, great! I can recommend some wonderful "off the beaten path" locations. But for the first-timer, I will start by admitting there is no perfect itinerary. And, follow with, 3 days is not enough time in Paris. But that is what I am asked to share. So if you have more time, this plan will still work with plenty of down time to wander or add another adventure. Highly recommend. And if you are unable to stay longer, this will help you see a good deal of Paris.

That said, I offer the following very ambitious 3-Day itinerary for Paris. It assumes you will not do everything, and that this is all the time you have for the City of Lights! 

First bit of advice, do some reading on being a guest in France.
For some more visit advice, see Advice for Visiting France for the First Time or Dining in Paris