Private tour guide in Paris

Context Paris is absolutely amazing. I've used Context Travel in multiple cities for at least a dozen tours and never had a bad experience. In Paris, one of the walking tours I took was through the Italian Renaissance galleries of the Louvre, and the guide was a curator for one of the other collections at the Louvre. Their guides are academically well qualified in relevant subject matter, interesting, with great English. The group tours are typically limited to 6, so they can adapt to group interests (and the guides almost always ask). They also do private tours. Check out their offerings on their website. And as an aside, their customer service, both in the US and the local city, is great. I've had to rely on it a couple of times-once when a Roman cab driver dropped me off in REALLY the wrong place for meeting the group, and once when there was a scheduling issue with the tour. They were available, helpful, and all turned out well.

Try Paris Walks.

Arnaud Servignat is excellent.