The Niagara Falls International Marathon is an annual marathon running competition from Buffalo, New York, USA to Niagara Falls, Ontario, Canada. Originally known as the Skylon International Marathon, it was first held in 1974, then had a ten year break from 1987 to 1996 before being relaunched in 1997. The course records are held by Peter Pfitzinger, who ran 2:17:10 hours in 1980, and Nicole Stevenson of Canada, whose time of 2:37:09 hours was set in 2004.

It is one of the few marathons in the world that starts in one country and finishes in another. Some other marathons cross international borders but return to the start, like the Monaco Marathon and the Unionsmarathon. The participants of the Niagara Falls Marathon have to show passport or NEXUS card at the start, which will be given back at the finish line or kept by the racer during the race.

The marathon begins in Buffalo, New York at the Albright-Knox Art Gallery. The first 6.5 kilometers (4.0 mi) are along the historic parkways of Buffalo before crossing the Peace Bridge into Fort Erie, Ontario, Canada. The remainder of the route is in Canada. After a very brief segment following the Queen Elizabeth Way, the route curves south and then north again along the Niagara Parkway, a landscaped road which winds along the Niagara River. Kilometer 42, the end of the race, faces the Niagara Falls on the U.S.-Canada international border in the city of Niagara Falls, Ontario.