If you only have a few hours in Montreal, stay in one area and walk. From a cruise ship, everything here is on foot. From the airport, getting downtown takes a big share of your time, so only leave if your layover is long.
From a cruise ship (Grand Quay)
Cruise ships dock at the Grand Quay in the Old Port, 200 de la Commune Street West, across from the Pointe-à-Callière museum (Port of Montréal). That puts you in Old Montreal as soon as you step off.
About 3 hours: walk up to Place d’Armes and visit Notre-Dame Basilica (the self-guided visit takes about an hour). Then walk Rue Saint-Paul east to Place Jacques-Cartier and come back along the Old Port promenade.
About 5–6 hours: do the above, then take a taxi or the Metro to Mount Royal for the Kondiaronk lookout, or to Atwater Market for lunch. Leave plenty of time to get back to the ship.
From a layover at YUL
The STM’s 747 bus runs from the airport (door 28) to downtown, stopping at Lionel-Groulx and Berri-UQAM Metro stations. The STM says buses leave generally every 10 to 20 minutes, and the $11.25 fare includes 24 hours of travel on the bus and Metro (STM). Traffic can make the ride a lot longer, so give yourself plenty of time.
Only leave the airport if you have time to get there, see something and get back through security with time to spare. If you’re connecting from an international flight, check the entry rules on the Government of Canada site first. With a short window, stick to one place: Old Montreal, or Downtown near the bus route. The REM light metro won’t reach the airport until its station opens, planned for 2027 (REM).
If you have more time
See 1 day in Montreal, or the airport to downtown guide for the full transit details.