Three days in Paris is the most common length of a first visit, and most three-day itineraries make the same mistake: they take a two-day plan and add more sights to each day.
The third day is not for more. It is for one thing you could not fit into two.
The rule
Two days gives you the historic centre, one museum and two evenings. The third day gives you a choice — and it should be a real choice, made before you arrive, not a list of leftovers.
Three ways to spend the third day
Versailles. The most common choice, and the right one if the palace and the gardens are why you came. It takes the whole day: travel out, the palace, the gardens, travel back. Go early, and do not plan an evening that depends on being back early.
A second museum, done properly. If painting or history is your reason for coming, the third day is the Louvre with a plan — one wing, three hours, then stop. Or Orsay and the Orangerie together, which sit close to each other across the Tuileries.
A neighbourhood you would otherwise miss. Montmartre in the morning before the crowds, or Saint-Germain and the Luxembourg gardens at a slow pace. This is the choice people regret least, because it is the one that shows them Paris rather than its monuments.
Pick one. Trying to do two of them turns the third day into the most exhausting of the trip.
The shape of three days
Day one: the historic centre on foot — Île de la Cité, the Sainte-Chapelle, the river, the Marais.
Day two: one museum in the morning, a neighbourhood in the afternoon, the Eiffel Tower from the Trocadéro after dark.
Day three: the one thing you chose.
Three days in this shape leaves an evening free and time to sit down. That is not wasted. It is where the trip stops being an itinerary.
What still to skip
The Museum Pass, unless your third day is a museum day and you do the arithmetic first.
The Eiffel Tower summit in high season, unless you have booked a slot.
Disneyland. It is a day on its own, and it is not Paris.
A second day trip. Versailles is one. Giverny, the Loire or Champagne each take another. Three days does not have room for two.
Who this does not suit
If you have been to Paris before, skip the first day and spend it in a neighbourhood you do not know.
If you are with young children, keep the third day light — a park, a carousel, the Jardin des Plantes. Versailles with a toddler is a long day for everyone.
If there is one thing you came for, put it on the first day, not the third. Weather, fatigue or a closure can take the last day away.
What we do not know yet
We do not publish opening days, ticket prices or queue times. Several major sites close one day a week, and it is worth checking before you decide which day goes where.
What does not change is the rule: the third day is for one thing, chosen in advance. Everything else fits into the first two.