Paris Charles de Gaulle Airport: Take RER B to Châtelet–Les Halles (about 35–45 minutes; roughly €13 for the airport fare), then walk 15 minutes to Bourse or change locally if your hotel is farther north. It is faster and vastly cheaper than a pre-booked shuttle; use a taxi only with heavy luggage or a late arrival (official right-bank flat fare is roughly €56, subject to revision).
Paris Orly Airport: Take Métro Line 14 to Pyramides (about 25–30 minutes; airport fare roughly €13), then walk 10–15 minutes into the 2nd or take a short onward métro connection. This is the cleanest route; do not waste time on a shared shuttle.
Paris Beauvais Airport: The official airport shuttle to Porte Maillot is the realistic option: allow 1 hr 20–1 hr 40 plus airport waiting time, and roughly €17–20 if booked online. From Porte Maillot, take Métro Line 1 east to Palais Royal–Musée du Louvre and walk, or continue by métro. Beauvais is not ‘Paris airport’ in any useful geographic sense; a late flight can turn this into a two-hour-plus transfer.
Gare du Nord: For Eurostar and northern TGV arrivals, take Line 4 south to Strasbourg–Saint-Denis, change to Line 3 for Bourse; allow about 20–25 minutes and a standard métro fare (about €2.50). If staying near Les Halles, RER B one stop to Châtelet–Les Halles can be quicker, but its passages are a poor first encounter with Paris luggage.
Gare de Lyon: Take automated Line 14 to Pyramides (about 10 minutes), then walk 10–15 minutes to Bourse or make a short connection. A standard métro fare covers it. This is simpler than crossing through Châtelet–Les Halles.
Gare Montparnasse: Take Line 4 north to Strasbourg–Saint-Denis, then Line 3 to Bourse; allow 25–35 minutes and one standard métro fare. A taxi is reasonable only if several people are sharing and luggage is substantial; traffic can erase any advantage.
Gare de l’Est: Take Line 4 south to Strasbourg–Saint-Denis and change to Line 3 for Bourse: around 15–20 minutes on a standard métro fare. Walking is possible in about 30 minutes if you travel light and want to start seeing the city.